Labino lecture 75 GAS
LABINO LECTURE '75 GAS. ( Courtesy of Henry Halem)
You can almost consider 'G.A.S.' as a ‘durability’ meeting. And it is not a bad word to remember. I don’t know what you all know about durability as such; it all stems on what you're going to use the glass for. So, if you hear me going on about putting distilled water in a bottle and leaving it there for a year, what happens to it is not exactly what you're going to be doing with ‘Art Glass.’ But, a bottle filled with pure distilled water in one year will pick up one milligram of sodium sitting on a shelf. And that doesn't seem like a whole lot but it's quite a problem if you're storing serums or other liquids that must be pure, or blood plasma or other things. So, all I'd like to tell you about is what A.S.T.M. says that water durability is. And so I'll be reading, and I don't have too much to read and I don't have too many slides but what I'd like to do is to show you what the amount of lime you should have and alumina for a reasonably durable glass.
A friend of mine had a large table lamp that he bought from a well known company which I will not mention the name, and the lamp was a sizable lamp - and he would clean it out; he only had it a year or two, no longer than that, and he said he'd take the thing apart and clean the inside because it was scummy, flaky scum on the inside. And if you notice bottles as the temperature changes, it sucks in air and when it gets hot it pushes it back out so you have a circulation of air and has moisture-it attacks the glass. So he said to me, "Nick, I have this table lamp. What would you do to it so that it wouldn't get dirty?"
I said my first choice would be to hit it with a hammer. The second choice would be to sandblast it so you couldn't see it. So he took the second choice and we sandblasted it. But this goes to show that ‘Art Glass’ although you're not putting liquids in it, and you're not storing serums and other chemicals that you don’t want to change in either PH or chemically, it’s still important in a way of ‘Art Glass’, And somebody says “Well what worry about what's going to happen to it 500 years from now”, as we were looking at some ancient glass last night of Dr. Brill's slides, I have with me a paperweight that was mailed to me from Akron, It was mailed to me by Jabe Tarter, and he said that he took this paperweight to Mrs, Daggenheart and she said that they washed it in a detergent that was too warm. The pits are about an eighth of an inch deep, and that takes a pretty good detergent! Well I took one look at it and I said “How old is it?” He said it's 20 years old and this lady had it on a bookshelf and took it down to clean it because it was dirty on the outside, I can't imagine what kind of a house someone would leave a paperweight for 20 years and then decide to take it down, but nevertheless, this is it.
I have cut a piece off the bottom and I told Jabe Tarter that there's only one thing wrong in my guess by looking at it and picking it up because it wants to stick to your fingers. It is mostly sodium silicate without any lime, I took a slice off of it and ground it up fine and boiled it. A normal glass would take about 2 or 3 millimeters of acid to neutralize it . This took 780 millimeters of liquid to neutralize it.
It might be of interest to you, and I dont know how many gin drinkers there are in the group, but gin is one of the alcohols that doesn't stay in the bottle without producing flakes. So they have to treat the bottles Inside if they're not a special glass to begin with. And what they do is drop a sulfur pill in the bottle right after it comes out of the mold. And the sulfur attacks the sodium and you get sodium sulfate which you wash out. And that keeps the gin from attacking the glass quickly, postpones it for a year or two.
And another solution that’s hard to keep in glass is magnesium citrate. And that one wants to attack silica glass for some reason or other, very rapidly. I’ll read what A.S.T.M. says about a definition of glass as to its durability. "It’s the lasting quality both physical and chemical of a glass surface. It is frequently evaluated upon prolonged weathering or storing in terms of chemical and physical changes in the glass surface or in terms of change in the contents of the vessel.
A.S.T.M. has a method of testing glass, they have various methods in Europe for testing glass. These are accelerated tests - no one seems to agree on which is a good one. But the best one that we know of in the States is called the A.S.T.M. C225 - 65.
65 is only the year that they agreed on another temporary method. They have a B.A. test and a B.W. test and a P.W. test. The B.A. is a bottle with acid and they titrate. The B.W. is bottles with water inside which they put into an autoclave at 221 degrees for 1 hour. The P.W. is a powder method with water.
Are you interested in how you make a test for water durability? Well I have slides that show the apparatus. And also charts that show how you arrive at a glass that is really durable.
This is a water durability of various glasses by the weight loss and electrical conductivity and titration method. This is a glass fiber and this is where I’ve had most of my experiences with glass fibers. The reason that I like to mention glass fibers is if you make a fiber, this is one micron, remember that, if you make a fiber that is one- tenth of a micron, one pound, the surface area will be 1.85 acres. There’s 42,000 square feet to an acre and this gets close to about almost 80,000 square feet-in that area of one pound fiber. The durability is almost tied into a curve that looks like the one that you're looking at. This is one micron fiber weighing one gram boiled in one hour in distilled water. And if you'll notice the bottom line, is resistance in ohms. In our audience we hare a lady with her last name being Ohms. And I almost fell over when she said that was her name. I like ohms. This method I've probably done more work than a lot of other people have on resistance of water change by boiling a glass and measuring the resistance before you boil it and after you boil it. The resistance of the water in this case is something like a million ohms. On the left is a weight loss and to your extreme left is a cc's of 50th normal sulfuric acid that it takes to neutralize the alkali that you leach from the fiber. And you can see that the curve is quite steep on some of the poorer glasses and some of the better glasses go all the way out to over 80,000 ohms.
Now this chart tells you a little bit more although you see this paperweight is not on there because this is only 8 and I told you this was 700 and something. But you'll see the ones on the left as indicated as poor - the ones in the center area as good - and the ones to the extreme right as very good. Now window glass is about 3,000 - that's what I call the area about here and I call those a little bit on the poor side and this goes for 'Art Glass' as well as it does for window glass. This method is not according to A.S.T.M. I have found flaws on the A.S.T.M. method because they're working in an area of glasses that fall in this area here, not here, and not here. The poor glasses, as you can see, the solubility goes up quite rapidly. The better glasses take off on a flatter curve.
You can also see that there are three things plotted here; one is the weight loss - the weight loss doesn’t mean too much unless you ignite the sample after you have boiled it and dried it. And the moisture, in some cases you have to go to over red heat to get out the water that has replaced the sodium that you extracted from the glass. But if you three tests you’re almost sure that you know what the durability is unless you’ve run a lot of other ones and that is by the titration if it's poor and the weight loss if it's poor and the conductivity if it’s poor, it must be poor.
This one I'm showing as four essential types of glass - I left out the phosphorous glasses because I don't think you have too much interest there - they are really soft - you really need a flashlight to find them when they're hot. The extreme left is a lime tableware. The row on the extreme right of the green one's of the tableware is a typical analysis of tableware. You notice the percent of calcium is about 9% - actually 8.9, so you could call that about 9%. The alumina to me would be a little on the low side. So I'm not telling you that I agree that this is a good one but I would call it normal lime tableware. And the potash and the sodium adds up to about 16. Now a good rule of thumb to remember is - if you have a total alkali of 16%, you divide that by 8, and that gives you what the alumina ought to be, and that ought to be 2%. Just a rule of thumb of a soda-lime glass in this area. If you're on the border line of having too high of alkali,for the amount of alumina and lime that you have, this is a good long working glass and a fairly durable glass but not what I would call very good. I'd say on the border line of good. It's been used for many years so tableware is washed so you wash off the scum and no one knows the difference.
The glass containers is another durable glass and you must remember that the containers is the cheapest form of glass that you can buy of anything except sodium silicate. I think it runs something like 4 or 5 cents a pound on a finished container so they can't put in too much in a way of cost and raw materials like B2O3 which is expensive, or zinc, which is very good in durability but also much too expensive. You see the lime then gets to be on a typical one that is extreme right gets to be about 11%. In recent years they have gone up in lime down in soda and the silicas about the same bobbing up and down between 71 and 74%. The alumina, you notice the low one with .4, they are now close to 2%. And this makes a fairly good durable, inexpensive glass. The potash lead glass is a typical full crystal glass not too far from what Steuben is doing. Steuben might be on the 26%, and the silica varies from 50 to 56, and the potash 10 to 13, an average would be around 15. Very durable glass, with a high index of refraction. The borosilicate glass is a very limited, and these might not be typical of the Coming 7440 I believe is their laboratory ware, but it's in this area, and you notice the limits are quite narrow, they're not bobbing all over the place, and the B203 is the high around 13. And the ones that Andy mentioned this morning around 15, if I remember correctly is getting up to the upper limit where borosilicate glassess are no longer durable. At 18% they are not durable and I sort of questioned, and will be anxious to make a durability test of anything that has 20% alkali and 15% B203 because the fluxes get to be 35% and that's a third of weight of the total glass, and that looks a little high to me but if Andy says they're good, I'll test them for him.
This is composition of Roman glasses and the alteration product according to Guenther. If you notice the unaltered glass which is glass that they started with, has 59 silica, 5.6 alumina, which is pretty high, remember if you divide it by 8 you get a pretty good figure. The iron is quite high, 2 1/2, calcium 7, magnesium 1, that’s around 8% again, the soda is a little high and the potash is a little high. So, the only thing that helps this glass because it’s still around yet, is the high alumina. And that’s why you can get by with that much alkali. Now I’ve noticed that the alteration products are, this is glass that is all flaky that Dr. Brill was telling us about yesterday showing what happens to it. The soda’s all gone, the potash is all gone; but what does it have - 19.3% water that replaced the sodium that left that glass. And so you have to ignite it on a dry basis, there you go. There’s no more sodium, it raises the silica, it raises the alumina and everything else as you would well expect. But the surprising thing is, that the sodium is all gone on the altered surface; this is not getting down to the solid glass, this is on that shell, which I’ll show you an example of later.
This is again two glasses that I think would be of interest because of the 1400 B.C. and the modern glass are not too far apart. And if you look, I don't know how many of you are familiar with Calley's book on Ancient glass - it has a very excellent review of glasses going all the way back to 1750. And these were some of the first analyses made and and to perhaps the last 10 or 15 years,of old ancient glasses by different people. And it’s surprising that the first chemical analysis was done on ‘Art Glass’ to find out what the ancients were doing. But the alkali in the 1400 B.C. glass was as high as 22 1/2 but you will also see that when the alkali is high, and those containers are still around, it’s because the durability was good enough to stand all these centuries. Otherwise they would have disappeared and heen no longer around to study. I think anytime you get over 16, 17% soda, you're looking for troubles. It might work good on the end of a blowpipe, but it might not look good several weeks from now, if it's in an atmosphere that has moisture.
This I put in only to show you about glass, since you are working with glass, I thought you ought to know percentage-wise what’s in a glass. The top one, where it says 75 - 15 - 10, I call a good glass. Very rounded figures, and the only variation you see is you might take out a little calcium and put in some alumina. But 75 15 10, is a good starting base glass. Now, if you look at the bottom, and break it down to oxygen, sodium, ions, calcium, and silicon, you’ll find, and wonder that you can't be right, you couldn’t have 92% volume on the end of a blowpipe having oxygen-but it's true because the ionic radius of oxygen is very high as compared to the other ions that are in the glass. So, you have 92% oxygen ions, 5% sodium, 2% calcium, and only 1% silicon ions in the glass by volume. Now by weight, these are in the ions form, 47% oxygen, 11% sodium, 6% Calcium, and 35% silicon. Isn't that strange? And that oxygen is what makes glass viscous.
This is an apparatus for measuring electrical conductivity. This is after you boil a known weight of glass in water. It gives you the reading directly in ohms before you start and after you boil It an hour and cool it back to room temperature.
QUESTION: Can you use an ohm meter?
You can use an ohm meter except you have to take the reading rapidly because an ohm meter runs on DC and so you get a battery effect that counteracts the solution. This is an AC bridge and it has two switches,and you have it on 60 cycles or you can put it up to 1,000 cycles where you don’t get any battery or polarization of the electrodes. So you get a more accurate reading by using AC but you can make yourself an AC bridge. I developed a little cell for measuring serum bottles that you couldn't get the large ordinary conductivity cells, for Owens-Illinois in 1940. In 1950 they were still using the same one. I was surprised I left in’46. The one that I developed you only need about 30cc's of liquid.
Now, I’ll tell you what to do to prepare a sample to measure the conductivity or a titration. The acid, as you see is in the buret on the right which is standardized to be 150th normal sulfuric acid. That, you can get out of any elementary high school chemistry book. The filtrate is done by grinding up in a steel mortar and a pestle and mortar again to get a ten gram sample that will go through a 40 mesh screen and not through a 50. So, it’s between -40 +50. That you put in water that’s distilled but half of it has been boiled away to take the CO2 out of it. Because distilled water wants to pick up CO2 out of the atmosphere so when you boil half of this water that has been previously distilled, you boil half of it away and then the CO2 is gone, then you go ahead and make your tests. The old test was done at 90 degrees centigrade for 4 hours. The new test is done for one-half an hour at 121 degrees centigrade. Then you titrate it by the amount of acid. If it's a good glass a± in l00cc's of filtrate, you should use about 1-2 millimeters of the solution on the right. I'm using a pressure cooker that holds something like 8 pints.
What's wrong with the test, as I see it, is that it only works for glasses in a certain area. Glasses that are very bad and I have one if you'd like when you're out tomorrow and I have time, I'll show you, I did it according to A.S.T.M., the grade size, the time, the temperature, and I turned it pink. You put an indicator, I failed to tell you, you put a methyl red indicator which is slightly yellow before you drop the acid in. You count the drops and it'll turn pink when you've neutralized it. And I've neutralized it and it's been sitting around for almost a week and every morning I look at it and it's not pink anymore, it's yellow, which means it's still leaching at room temperature. And that's for a bad glass and according to A.S.TM I could have gotten a figure and say, “well this is not as bad as it looks”. It's actually worse than it looks! I'm maintaining now that boiling is still the best method because boiling does stirring, and you get a lot of movement that you don't have at 121 degrees centigrade in a pressure cooker because it's laying there, there's no activity.
This is a old bottle I think a jug, I presume, Syrian, and it dates back to maybe 4th to 5th century AD, and it's very light- it was light when it was made, but it's much lighter now. It's very thin on on side . You can see that it's rusted away like a tin can. And I took a flake off of this and ground it up fine , boiled it in water, and it's very good in durability. Because of the charts that I showed you earlier: all the alkali has been leached out, so it ought to be good. It’s a manganese glass, I presume it was manganese when it was made. This was in a moist atmosphere so it had a lot of water so you had a lot of reaction of the glass. Very, very thin, very, very light.
Now here's where you can learn something about what you ought to do in the way of compounding glasses. If you notice on the extreme left is the sodium oxide dissolved. The next vertical line is the normal sulfuric acid used in millimeters. If you'll notice, this chart goes up to 25. So, you'll want to stay away from anything that is much more than 10 or 12. This is all for glass that has 8% calcium oxide, and the alumina varies with these other lines. I consider 8% lime the lowest limit you should have for a fairly good durable glasses that you don't have to worry about. If you pick out a glass that has 2% alumina which is R2O3, 8% lime, 15 or 16% sodium, and the rest is silica, you'll have a good glass. If you would blow any glass that you thought was a poor durability, you let it sit in the atmosphere and you get a film on the inside of it in less than a week. And if you put a good glass next to it, it'll still be clear 2 weeks, 3 weeks later. Id' hate to sell a piece of glass and put instructions with it; "Wash off every two weeks with a mild detergent."
This is glasses with 2% alumina. And R203 means it's alumina and iron. And you know you don't have the iron very high so that's mostly alumina. And this is varying the lime contents but you see what's happening again if you pick out a line there - 6% jumps up pretty rapidly at around 17, 18% sodium.
QUESTION: We generally try to avoid: getting iron into the glass. Does the iron play an important role in durability?
Iron does not play an important role in durability unless you have at least 7%.
Recording ends here.
Where are we going and why am I in this basket?