Glass engineering - designing and making photochromic glass-----make money online

today on Applied Science I'm going to

talk about designing and creating small

batches of glass this is an unusual

branch of engineering it's very unlike

electrical or mechanical in that there's

basically no information available how

to get started in the home shop so today

I'm going to summarize everything I've

learned in the last couple months

including reading out of print books and

talking to glass experts and show you

how to start having fun with this right

away okay so let's check out some demos

let's take a look at this unusual piece

of glass I'm going to shine some light

on it from this blue laser pointer that

I got from eBay let's see what happens

as you can see the glass is actually

changing color when I shine light from

the laser pointer in there and it's

fairly responsive it changes in a few

seconds this glass is actually

photochromic so it's basically the same

kind of glass that is used in sunglasses

that change color when you go out into

the Sun and some regions ever are a

little bit more sensitive than others

but you can definitely see what's going

on here right let's try this one

this one's also photochromic we can also

give it a blast of light from this

really big ultraviolet flashlight that I

have here let's try this one out this is

about the same wavelength 405 nanometer

as the laser pointer it's just more it's

just more of it there's there's more

LEDs in here and then just for

comparison this is like a modern

photochromic lenses that these guys

donated to the channel a long time ago

just so you can see the performance

difference so a modern this is actually

a plastic lens and so it's not quite the

same chemistry in here but you can just

get an idea of of how it works with a

modern photochromic lens dies in plastic

as opposed to glass and now all of these

are actually reversible so if we wait

around long enough both the commercial

lens and the glasses that I've created

are they'll eventually go all the way

back to their original state now in the

commercial lens this happens in

hopefully five to ten minutes in the

glasses that I've created it's quite a

bit longer

could time-lapse this but it's really

kind of like an overnight thing for this

to translate back to its original

clarity pretty cool though there's

nothing special about this laser pointer

I'll put links to everything as always

in the in the description you can go on

eBay and just pick up one of these laser

pointers okay

so that's this is actually making this

piece of glass took a long time let me

tell you most of the samples that you've

seen on this table here were me

attempting to make photochromic glass

and it's taken a long time because

there's a lot of variables involved here

and I'm very happy to get this level of

performance so this is not anything

shocking I mean it's been around since

the 1950s or 60s

however I'll bet you have not seen a

piece of glass that works quite like

this one this one is also photochromic

but as you can see the fade time is just

seconds and so if I go across like this

you can see it's there and then it fades

this is actually an opal glass and so it

it is a piece of glass it's just it's

not transparent and it has this really

weird property where you can draw on it

and then it fades away almost instantly

just a few seconds and the top has this

weird kind of crystalline thing going on

but it also works about the same way

almost unfortunately this was a batch of

glass that I made just by throwing a

bunch of leftovers together in a pot so

the point the formula for this one's

unfortunately lost the time forever but

the point is that I want to get everyone

into hacking glass because with you know

as many people hacking on electronics

and mechanics if they were all hacking

on making glass we would have all kinds

of weird stuff by now so let's start

talking about how to do this when I

first got started with this project I

thought what I would do is get a mold a

glass mold dump all the ingredients in

there with a mold release heat it up

cool it and then pull out my finished

piece of glass however it can never work

that way unfortunately and the reason is

that the glass batch when it's being

formed like going from a mixture of

powders into a finished piece of glass

is extremely reactive and all of the

mold releases that you can put in here

will actually get sucked up into the

glass batch and then you won't have a

mold release anymore there's only one

material on earth

that won't stick to melting glass or

forming glass and that's platinum and so

they actually make tiny little platinum

crucibles for doing laboratory glass

analysis but that's a little expensive

and apparently from what I've heard even

then the glass doesn't just fall out I

mean it still sticks in there and so if

you're hoping to make like a nice you

know good-looking puck of glass it's not

gonna work forming it in a mold like

this so I'll just cover that the mold

releases quickly if you do make a custom

blend of glass and then you want to form

it into an interesting shape then you

can use these conventional mold releases

and most of these things came from like

an art supply house for glass artists to

popular kinds of mold release are this

primo primer and this is a powder in

here that you mix with water and it ends

up making this fun purple solution and

the purple is actually a useful thing

when you're brushing it on your mold you

can tell the spots that you haven't

covered because they aren't purple so

that's the point of that and then I also

tried this really expensive boron

nitride mold release this is actually

really great stuff it's also fifty

dollars it can and it works really well

but again if you're making glass the

temperatures are really high and the

glass is very reactive and it will

actually suck the mold release into the

glass batch and that's actually what's

happened here so this was a mold that I

coated with that boron nitride spray and

I put my ingredients in here and what

happened this brown color is actually

the boron nitride that's been

incorporated into the glass and then

after the glass was done eating away all

of my mold release it proceeded to stick

itself permanently to the mold which is

alumina so what happened here is I

basically just glazed the mold I started

with this unglazed piece of alumina and

now the glass is permanently fused in

there so the way to do it is to get a

melting dish and I'll put links again to

all this stuff these are these you can

actually buy these on Amazon they're a

little expensive on Amazon if you get

these imported you know from a Chinese

seller on eBay it's just like a buck or

two I mean it's no big deal

and you can take these up to very high

temperature

and what you want to do is put your

glass batch in here heat it up and then

pour it out onto something else but

we'll get into the details later also I

should point out that you might have

heard of float glass so commercially if

you want to make like a big sheet of

glass and make sure that it's really

flat what can you do you don't want to

put it through rollers because the

rollers you know might Mar the surface

or you have to adjust them to make them

really parallel so the way the glass is

made commercially is a giant vat of

molten tin and they pour the molten

glass on top of the Bolton tin and

because gravity is makes things flat at

the small scale here you're guaranteed

that everything will be flat and uniform

because you're dealing with liquids on

the surface of the lake right it's going

to be flat there's a couple of

interesting crowded of course inside

here I've got some tin I bought tin

pellets on eBay and put them in my

crucible here and melted it and then put

some glass on top and you can see it it

kind of almost worked but there's a

couple of interesting problems one the

tin oxidizes if you just heat it up in

air so commercially what they do is have

a giant furnace full of hydrogen gas

where this liquid tin is hanging out and

the hydrogen gas is very reducing it

basically prevents oxygen from from

being in there because if any oxygen got

in it would react with the hydrogen so

needless to say this is getting to be

kind of difficult to do in the home shop

having a

molten tin with hydrogen gas and

everything and then another interesting

problem if you're making photochromic

glass for example you can't do it in the

float glass process because this glass

is very sensitive to the environment

it's in and it really doesn't like

hanging out in a hot hydrogen

environment because it actually prevents

the glass from being photochromic so

this can only be formed in crucibles or

in oxidizing environments you can't use

the float glass process for this so

originally when I was having this

problem with the glass sticking to the

the molds and I was wondering what to do

I thought well maybe I'll try this

liquid metal idea since how could it

stick to liquid metal and I would

recommend not bothering with this at all

as it turns out if you want to make a

flat piece of glass in the home

shaf there's easier ways to do it just

forget the tin it's it's actually not

that helpful if you're in a bind and you

can't find or afford these aluminum

melting dishes it's also possible to use

porcelain so if you go to the store and

buy you know dishware just plain old

porcelain destroyed this can be okay the

temperature that this can sustain is

just barely high enough to do some glass

experiments and we'll get about you know

we can talk about making the glass melt

at low temperature so that you can use

porcelain melting stuff the one thing

you have to be careful about is that if

you buy dishware from the store it's

already glazed right so there's already

glass inside here on top of the

porcelain you can feel the difference

like if you touch this part of it it's

typically not glazed so that's the raw

porcelain and then inside it's already

covered with glass so if you're making a

glass batch and you pour all your

ingredients in here it's going to be

mixed along with whatever glaze the

manufacturer already used whereas if you

if you go with one of these unglazed

melting dishes this is really raw

there's there's nothing that this is

going to contribute to your glass batch

shirts

it's the minimal amount okay so you've

got your aluminum melting dish or your

porcelain demitasse and you're ready to

put it in the kiln to melt all the stuff

down so let's talk about kiln selection

first gas versus electric in this

tabletop small scale size there are no

commercial gas kilns so you'd have to

make one but that's you know not the end

of the world there's a couple other

considerations though - you want your

kiln to have really good temperature

control like plus/minus 10 20 degrees C

because a lot of making unusual parts of

unusual kinds of glass involve heat

treatment and annealing and you really

do need good temperature control to do

this so you know really fine temperature

control with a gas kiln is it more

difficult you probably need to like

throttle the gas down not just turn it

on and off to get good temperature

control but the last consideration and

sort of the most difficult one to get

around is the atmosphere inside the kiln

remember I was saying that having

hydrogen atmosphere is no good for

photochromic glass so they actually

chemically hurt the glass and prevent

it from being photochromic if you have a

gas-fired kiln the exhaust from your

flame is actually reducing there's

probably quite a lot of carbon monoxide

in there and at these temperatures that

carbon monoxide will find oxygen

molecules and react with it to make

carbon dioxide and it's so reducing at

these high temperatures that it will

actually pull oxygen out of the glass

and prevent it from being photochromic

so I don't know I think commercially you

could probably get around this by having

like a really big crucible inside your

gas-fired kiln and it's only the surface

layer that's affected by the reducing

atmosphere and a gas-fired kiln the

trouble is if you're using small little

melting dishes like this the amount of

surface area appears high enough where

if you've only got you know 100 grams of

glass in here it's basically all going

to be affected by the atmosphere in the

kiln so using an electric kiln is very

nice because temperature control is much

easier and if you open the lid to the

kiln you're guaranteed to have

atmospheric air inside there later on

you'll see there's so many variables

involved with making a piece of glass

that eliminating one more variable of

having this unknown atmosphere from a

flame in your kiln is another thing

especially if you're turning the flame

on and off to control the temperature

now you're controlling also the oxygen

level because the flame is on and off

and so then there's more or less oxygen

I would recommend definitely going with

an electric this particular kiln here is

called a muffle kiln and it's built kind

of funny it almost seems like a DIY

project itself it's basically just this

helmet shaped thing and they can see the

heating elements inside there and you

can put it down on any surface you want

and sort of turn that into a kiln this

is the Paragon quickfire I bought this a

long time ago it's not sponsored of

course this is about three hundred

dollars new I think and it's actually a

really good solution the heating

elements are rated to go up to about

1050 degrees C but I've pushed it to

1150 no problem one consideration is

that it just comes with a switch

so the the original temperature control

is a switch that you turn on and off

yourself and a analog temperature gauge

here to tell you how hot it is and

that's not going to work for doing a

glassy treatment or annealing so what I

did is I added this little pig

controller here and you can set the

temperature and it's actually amazingly

good at reaching a temperature and

holding it within just a few degrees

even the reason that this kiln is

limited to maybe 1150 C or even 1250 if

you really really push it is because the

heating elements themselves are made of

nickel iron right nichrome and

eventually it melts so it's a pretty

hard limit on how hot you can get it

because your heating elements eventually

get so hot they melt so that that really

does put a cap on things and

unfortunately most silica glass patches

have a rated like melting or forming

temperature of like 14 or 1500 degrees C

which is much too hot you'd never get

your night chrome furnace that hot so

what do you do well there are actually

special electric furnaces that have

heating elements that are not made of

nichrome so the next level up from

nichrome is silicon carbide is actually

conductive and it melts at a higher

temperature so they make heating

elements out of that and then the top of

the line is molybdenum disulphide very

unusual material that's a blend of

molybdenum and silica and they make

these very very expensive small heating

elements out of this material and you

can get a kill on an electric kiln that

goes up to fifteen or sixteen hundred

degrees C the downside is that these

kilns are really expensive even you know

cheap import models on eBay sell for

like two or three thousand dollars so

you know it's in the context of this

video it's really just kind of out of

reach I wouldn't worry about it the nice

thing is that you can make glass

formulations that just don't require

that kind of temperature so there's a

lots and lots of experimentation you can

do without father and with any of that

and that's what we're going to talk

about in this video this kiln originally

came with its own shelf like its own

bottom and you can see what happened

here now remember I said that glass is

very reactive so if you spill a little

bit of

glass batch on the Shelf here and then

heated up to high temperatures it's

actually dissolving away the material of

the kiln itself so you have to protect

the kiln and everything in there from

your from your glass even spilling it is

actually a very damaging like corrosive

kind of event so luckily this this

material is not super expensive and the

nice thing about these muffle furnaces

where you sort of pick the whole furnace

up is that you can just have like a new

bottom every month or whenever you need

it so you can buy these fire bricks that

are very lightweight and can take very

high temperatures and are also

insulating so I'll put links to all this

if you search for fire brick be careful

because some fire bricks are rated for

high temperature but they aren't really

insulating like it can withstand fire of

it it's gonna get hot on the other side

whereas it brick like this it could be

you know 1,400 degrees C on this side

and you could put your hand on this side

and it would be no problem so to repair

this kiln but I do this I just put two

of these standard sized insulating fire

bricks here and that's now my kiln floor

another thing you can do to try to

promote the life of your kiln floor is

to cover it with this special kiln paper

so they sell this stuff at the art

supply stores and watch watch how it

works

pretty cool it's paper that doesn't

really burn and so if you put glass on

top of here this axe is sort of like a

buffer layer and this will eventually

become completely white ash and the

glass won't be able to stick to the kiln

floor because there's this layer of ash

in between so pretty handy stuff just

keep in mind though that if you pour

your glass batch like if there's powders

on here that are gonna form a glass they

will dissolve the paper and the ash and

everything else like we mentioned and

eventually get all the way through so

this is sort of a low-level way to

protect yourself from spills you can see

in my in my kiln here there's all kinds

of remnants of ash here since I've been

putting kiln papers on here to try to

protect the top not 100% though because

you can still see little errors here and

there

oh also you can use sort of a trivet so

what will happen is the glass is very

viscous and sticky and so if you've got

your melting dish like this eventually

you'll get some running down the side

here it'll dribble down and if it's just

sitting on top even with the kiln papers

it'll eventually make a huge mess and

destroy your kiln floor so you can put

like a porcelain or alumina tray here so

that when you put this down the drip is

at least caught by that you keep the

kiln floor living a little bit longer so

we talked about making your glass batch

in an alumina melting dish like this and

then pouring it out on to a surface

there's actually a really great material

for doing this and that's graphite so if

you go on eBay or Amazon you'll find

there is these graphite Casting molds

mostly for metal actually they weren't

thinking that you'd use this for glass

but you can and what I found to work

really well is to get a mold of about

this size and put it down like that you

can use sandpaper to get the surface

really flat and then use like a paper

towel to polish it and then when you're

getting ready to pour your glass what

you do is you the surface up with a

torch till you know it's maybe a few

hundred degrees C or maybe even five

hundred and then obviously there's gonna

be hot open the kiln up and take your

glass and pour it out onto the surface

and the nice thing is that the graphite

will not stick to your glass hardly at

all I mean it's a really slippery

surface what I found out doesn't work

don't do this don't take the whole thing

and put it in your kiln and then close

the lid and heat the whole thing up to

kill them temperatures the the graphite

will survive

but what will happen is the glass will

rip off the top layer and it again

incorporate the graphite into the glass

because it's so reactive so that doesn't

work okay so we've talked about the

melting dish the kiln the mold release

and everything what do we actually put

in the dish to make this glass this is

where things get really weird so if you

search for patents about you know how to

make weird kinds of glasses let's say

photochromic glasses you'll find lots

and lots of very detailed glass analyses

right so you'll typically see let's say

you find a glass analysis it's 50%

silicon dioxide

you know 40% boron trioxide 10% sodium

oxide great I'll just get you know 50

grams of silica 40 grams of or 8 and 10

grams of sodium oxide and mix it all

together and make a glass right not even

close

the ingredients that are that go into

the glass batch do not have a whole lot

to do with what comes out the other end

and this may seem very strange but

there's a really great analogy and

that's in cooking so if you analyze the

piece of cooked bread you would say it's

you know 20 percent gluten 20 percent

water whatever it is but if you're

explaining how to make a blow for Fred

to someone you wouldn't use those terms

you would say start with flour and water

and it's actually the process of making

the bread that develops it into gluten

and all the other finished products and

that's that's exactly what's happening

with the glass one trick with making

these glass batches is that the

temperatures are so high that almost any

carbon is going to go away it's going to

react with oxygen and leave the glass

batch entirely so if we for example put

in lithium carbonate when we heat this

up to you know 1200 degrees C the co 3

is going to go away and the oxygen is

gonna there are some of the remaining

oxygen

is going to react with the lithium and

we'll be left with lithium oxide in the

glass so and then you might say well why

not just start with lithium oxide the

problem is that lithium oxide is really

reactive and so if you put that in the

glass batch it's very possible that as

the thing is heating up all that lithium

oxide is also going to go away before it

has a chance to be incorporated into the

glass batch so choosing ingredients to

make a glass sort of requires you to

find an ingredient that has a melting

point and a stability that is compatible

with all the other materials in glass

luckily a lot of this work has already

been done so if you sit down and you

know you want to put lithium in your

glass you pretty much use lithium

carbonate there might be a few other

chemicals that work too but pretty much

it's always lithium carbonate and also

for example if you want to add sodium to

your glass pretty much using sodium

carbonate is the way to go okay

unfortunately there's not like a master

table or anything that I have found that

lists all the possible things you can

put in I mean there's literally hundreds

it goes on and on but to make sort of

more normal kinds of glass it is pretty

well figured out and I'll put as many

links as I can in the description to

help you out when you're just starting

out and making a relatively simple kind

of glass just plain old clear glass I

would recommend is doing twenty grams of

silicon dioxide 20 grams of sodium

carbonate and 20 grams of boric acid and

this will make you a borosilicate glass

you've probably heard that term before

it's the same kind of glass that's used

in glassware and cooking dishes and all

this kind of thing one benefit of

borosilicate glass is that it is less

sensitive to temperature fluctuation

right like you don't want your glass to

crack if you're heating up a test tube

or something like that and similarly if

you're making glass on your own you

actually don't want it to be very

temperature sensitive because you're

gonna have to cool your piece of glass

down from kiln temperatures all the way

to room temperature and annealing is the

process where you pick a temperature and

hang there for a while to let the glass

relax and sort of all the stresses

dissipate and it typically takes hours

for this to happen but having

borosilicate glass you still have to

anneal it but it's less

sensitive than a non borosilicate glass

or something that's more sensitive to

temperature fluctuation mixing up all

the powders is pretty important and it's

something that I haven't spent a huge

amount of time on but I probably should

what I typically do is just have the

container on the scale put all the

powders in it and then sometimes I'll

add these to brass balls and put the

container lid on and shake it around and

the balls will help sort of stir up the

powder and actually kind of crush some

of the crystals a little bit to mix it

up

in reality this could be a lot better

any what you really want to do is put it

in a rock tumbler and run it for a day

or an hour or something like that and

that will make sure that the powders are

really really well mixed together and

this is important because like we were

talking about the glass batch doesn't

just sort of all melt together it's

actually a chemical reaction that's

happening in there so you really want

the powders to be in really really well

mixed intimate contact with each other

so that the chemical reactions can

proceed as smoothly as possible if

you've got a clump of something off in

one corner of the crucible it's possible

it will eventually melt and make a glass

for you but it may not have the

properties that you want because it

didn't properly react with all the other

ingredients and again think of a loaf of

bread right like if you have a little

chunk of unmixed flour or something in

one corner of the pan yeah you'll still

end up with a loaf of bread or something

but it's not gonna be as good and funny

enough the analogies with cooking

continue this is actually a good

ingredient to put in your glass just

plain old table salt

will add sodium and chloride and both of

those are actually important in making

photochromic glasses and so it's no joke

that you know if your soup isn't very

good what do you do you know you put in

a pinch of salt same can be true of your

batch of glass the main components of

the glass are not super sensitive to

variations in ratio so for example if

your glass is 1/2 silica and about half

bori you know getting it to be 4951

isn't going to make any difference but

when you're making them glasses that are

photochromic or have like a very

sensitive chemical aspect to them some

of the ingredients are very sensitive

and the quantities are just absolutely

tiny so for example in the photochromic

glass

this copper oxide needs to be added

about point oh eight percent I think and

so measuring out such a teeny amount

even with a balance that's capable of

measuring milligrams is very challenging

so what you do is you dilute the

sensitive ingredient in one of the base

ingredients so for example for this

borate glass I'm using boric acid as

like the main batch component and so

what I would do is take half a gram of

copper oxide and mix it with 20 grams of

borate and so I'll have this very dilute

sort of copper oxide powder and then you

can measure this out with also still

pretty good precision but not quite the

precision that you need to measure the

oxide by itself let's finish up by

talking about the actual chemical

ingredients that go into this

photochromic glass sort of as an example

and I'll try to describe and generalize

what these ingredients do so this

winning combination that I've got here

this photochromic glass has this recipe

it's 22 B as you can see I spent a long

time tweaking different components of

the recipe there are a lot of variables

involved here not only is the ratio of

ingredients important but also the speed

at which you bring them up to the

melting temperature in the kiln and then

how long you hold it at that temperature

and then when you pour it out of the

kiln you let it cool down to room

temperature and then bring it back up to

a forming temperature to actually create

this photochromic property and then of

course that has a time and temperature

associated with it as well and the

atmosphere and the kiln during the melt

process and then the atmosphere during

the heat treat process and it just goes

on and on so I'm not claiming that this

is tweaked it down to perfection in fact

far from it this will just give you an

idea of what's going on and sort of the

the challenges that you'll encounter if

you end up doing this I should also

point out that a lot of the patents

around photochromic glass talk about a

lot of these times and temperatures but

they'll say things like the heat

treatment may be conducted between 500

and 700 degrees C for between ten

minutes and two hours now what will

actually happen is that the heat

treatment only works between 600 and 600

twenty degrees and it must be between 30

minutes and 40 minutes

but of course they want the patent to be

as broad as possible and if there's some

weird way you can make it work outside

those parameters then fine but they're

definitely not describing the easiest

way to make it they're describing all

the possible ways to make it and so

that's kind of another problem with the

patent system is that it's you write

them to be overly broad but anyway okay

let's get down to business here with the

chemicals this winning combination is a

borate glass there's actually no silica

in it whatsoever so it's not

borosilicate it's just for Oh borate

glass so we've got 20 grams of boric

acid this will contribute b203 or borate

in the final glass and this is kind of

the backbone of the whole system then we

have 2.2 grams of aluminum hydroxide now

remember the hydrogen is going to go

away at these high temperatures and

we're going to be left with al 2 O 3 so

alumina which is dispersed among the

mixture and the function of alumina is

just to stabilize the glass structure we

don't want it to diva trophy which means

convert from a glass into a crystalline

structure and this helps with that this

ingredient also calls for calcium

carbonate which again the carbonate is

going to go away and this is going to

become calcium calcium oxide in the

final glass and this is also a

stabilizer that makes the glass less

dissolvable like less prone to being

broken down by the environment I know

that sounds silly for a glass that we

only care about you know I just want

this to work in the lab I don't care if

this survives for years and years but

again I was following a recipe and I got

this thing locked in and I couldn't

change this variable easily because I

was too busy changing other variables

basically then we have 0.4 grams or 0.3

grams in the winning mixture of silver

nitrate this is actually the same

chemical that works in old-fashioned

black-and-white photography and it's

actually the same mechanism inside the

photochromic glass so what happens is we

mix silver nitrate with sodium chloride

in this glass mixture and then as it's

reacting as the glass is being formed

these things trade places and we end up

with silver chloride and sodium nitrate

and the sodium nitrate gets burned down

into sodium oxide and

trait goes away and we're left with

silver chloride and I have a little bit

of silver chloride over here let's take

a look we zoom in so there's some silver

chloride and if I shine this ultraviolet

light on it again check out what happens

look at that it turned dark just like

the photochromic glass so basically

we're just dispersing the silver

chloride throughout the glass and that

same process that you just saw is

happening in the glass which causes it

to darken the reason that it becomes

dark is because the silver chloride when

it gets hit with this moderately high

power light it's not quite ultraviolet

that it's pretty close actually converts

into metallic silver and so that dark

color is silver metal as opposed to

silver chloride so if we had a glass

that changed from clear to dark only

once in its whole lifetime it never went

back to clear it wouldn't be that useful

as a pair of sunglasses so we add

another ingredient copper oxide in a

tiny quantity I've written down 0.1

grams but this is actually a 40 X

dilution so we're really only talking

about you know 2 and 1/2 milligrams of

copper oxide for this whole batch of

glass it's considered a dopant because

it's in such small quantity and what

happens here is that it accepts

electrons from the silver chloride so

when you hit the silver chloride with

light it converts to metallic silver and

I think gives up an electron don't quote

me on that

and then the copper oxide accepts that

electron and then pushes it back into

the silver metal causing it to go back

to silver chloride so this is sort of

like a reserve of electrons and copper

oxide has the correct sort of affinity

for this to happen properly I believe

the copper oxide is also chosen because

it works over a large temperature range

so you'll notice that with normal

photochromic even commercially made

photochromic sunglasses at very cold

temperatures they will not become clear

very quickly like if you put it in your

freezer it may take months or weeks or

something to become clear where is it

high temperatures it works pretty well

and the copper oxide is responsible for

reducing that temperature dependence and

then we have sodium nitrate this is an

oxidizing

so when this breaks down in the high

temperatures of the kiln it releases

oxygen gas and this is important because

there could be a fairly strong reducing

environment in there or there could be

and we don't want that to happen because

if there's a reducing environment our

silver chloride or while this is being

formed the silver actually might be

reduced down to metallic silver before

the glass is even done being formed and

you can actually see this in previous

glass batches I had a problem with

little silver droplets being formed in

the crucible obviously this is no good

because we want that silver to stay in

solution for it to give us this property

and then finally I'm not sure if this is

critical or not I started adding sodium

silico fluoride to some of these batches

and the winning batch actually did have

a little bit of sodium silica fluoride

and the idea with this is that it

provides a nucleation center for the

silver chloride to form so the trick

with this heat treatment after making

the glass is that we we have these

silver chloride atoms distributed

throughout the glass it's sort of like a

photograph but it needs to be clear in

its clear state so there can't be too

many of these silver chloride atoms or

parent molecules so what we do is we

heat treat the thing and the silver

chloride we want to aggregate into

bigger chunks and that way they can

actually convert into metallic silver

and give us this great photochromic

property so what we do is add some non

dissolvable stuff these fluorides are

apparently not dissolvable in the glass

they're still clear but there's like

little pellets sort of distributed

throughout the glass and they provide

like a convenient source of condensing

for these silver chloride atoms to start

forming clumps so if you're having

problems getting the silver chloride to

clump you can add this and that will

help out the process if you don't want

to add the fluorides you have another

option to create these nucleation

centers what you can do is just keep

adding so much silver nitrate that

eventually all the silver chloride

that's going to form has formed and then

there's actually excess silver left over

and what will happen is the excess

silver will just hang out in the glass

and so it actually starts out kind of

dark basically the silver provides it

own nucleation centers and this one is

actually photochromic as well the trick

is that it just starts out kind of this

this reddish color because it's actually

silver nanoparticles that are

distributed throughout the glass giving

it this nice color actually so if you

want sunglasses that go from dark to

really dark that's this is the one for

you I forgot to mention that a lot of

these ingredients are volatile at really

high temperatures so we're in the kiln

it you know 1200 degrees see the silver

is not just hanging out in there the

silver is actually evaporating away at

1200 degrees C so to make matters even

more difficult after you've come up with

this you know special formulation if you

were to put all these ingredients into

one of those tiny melting dishes and

left it there overnight at 1200 degrees

C you wouldn't have any silver in there

left what so ever and your glass would

not be photochromic and so it's a really

good balancing act difficult balancing

act between getting the process set up

correctly such that you put in enough

ingredient and then cook it for long

enough such that just the right amount

of ingredient is left over at the end of

this process and it makes it very

difficult if you're using small batches

so if you do this yourself I would

recommend me using bigger melting

containers than I am so I'm making these

like tiny you know we're starting with

20 grams of bori this whole glass ends

up being about 20 grams because all this

carbonate gets burned off so we start

with maybe 30 grams of ingredients or 30

something and we end up with 20 grams of

glass that's really not very much and

the fact that the melting vessel has

like a lot of surface area to it means

that a lot of the silver is burning away

so you're basically talking about making

a soda and then leaving it on the

counter and waiting for it to go flat

but not too flat and then stopping it at

just the right point so that you have

just the right amount of ingredients and

remember that you know the silver is

going to volatilize that a different

rate than the other things are so if

you're trying to control the ratio

between silver and copper for example

and the copper is not volatile or it's

only a little bit volatile and the

silver is really volatile then there's

like this very narrow process window and

so it's it's a lot of tweek

I've made you know I'm probably 50

batches of glass over the last few

months and I found the process to be

kind of fun but also maybe a little

frustrating but I guess that is part of

the fun of it oh one last thing how do

you get these cool colors these are all

special oxides that can be added in

really small quantities and so this is

actually copper oxide so if you put in a

lot more copper oxide than two

milligrams let's say you put in like

actually 0.1 grams of solid of pure

copper oxide you end up with glass that

looks like this this one is chromium

chromium oxide is green and also

interestingly you can control the color

of it based on its oxidation state this

deep blue one is copper oxide when it's

oxidized as hard as you can I think it's

like two-plus maybe and then this is

also copper oxide that is neutral or

even slightly reducing so this might be

like one plus or something and a lot of

these oxides have two colors that you

can get to with different oxidation

states okay well I hope that was helpful

and feel free to ask me any questions if

you get into making glass and I will see

you next time bye earn money online by typing pages, earn money online daily, online work at home and earn money, online earning, earn money online free, online money earning sites, earn real money online, e commerce ideas to make money, easiest way to earn money online, best way to earn money online, make money from home, make money online free, money making sites, earn from home, real ways to make money from home, online income ideas, make real money online, top online earning websites, earn money online fast, top 10 money earning websites, earn money without investment, earn money online for students, best sites to earn money, make money online 2019, earn easy money online, earn money online instantly, real money earning sites, make money from home online, make money online fast, earn dollar online free, online earning ways, best online money earning, earn money online with surejob, make money online, online money making sites, best sites to make money online, earn money online paypal, online earn money by typing, best survey sites, ways to earn money online, ways to earn money from home, make money online without investment, make money online surveys, 

s