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View Full Version : Coated glassware, crucibles & retorts



thrival
04-05-2013, 09:40 PM
This is but a small victory for me, but an important one. Obtaining labware that can withstand high temperatures and at low cost, determining what you need without salesmen or being nickel & dimed to death, is a challenge for beginning alchemists. While I did invest in a full lab distillation apparatus on ebay a few years back (on sale for $80. USD) it didn't come with supports or clamps, and I never really figured out how to set it up. It seems to take up a lot of room. Then there's the whole learning curve of working with ground glass joints. Reading Glauber, I was impressed with his resourcefulness for creating his own crucibles & labware. One of his inventions outside of his writings, because he didn't publish it himself, is a recipe for coating glassware, crucibles & retorts to withstand raging fires.

So I was playing with this recipe, which is a mixture of iron powder, sand, fire-clay, and a pinch of sal ammoniac. I made a dixie-cup test and the material set up as hard as a piece of steel slag. So I took a tempered gal. glass jar and coated it with this mixture. The material has almost completely hardened without cracking. So now I have a vessel I trust can withstand boiling acids, for reclaiming, and digestions. This material is also good to coat clay retorts used for dry distillations, and permanent lutes that will never come undone.

http://img835.imageshack.us/img835/8497/coatedjar.jpg (http://imageshack.us/photo/my-images/835/coatedjar.jpg/)

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http://img145.imageshack.us/img145/6092/distillapparatus.jpg (http://imageshack.us/photo/my-images/145/distillapparatus.jpg/)

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Karl
04-06-2013, 01:37 AM
Wow! Exciting Thrival. I'm really surprised it isn't cracking. Have you heat seasoned it yet?

thrival
04-06-2013, 02:35 AM
Hi Karl.

No I haven't heated it yet. It could still crack, I may have added a bit too much clay vs. iron, but if it does, I'll just etch the cracks with a pointy nail and fill with the same material, to see if it sticks to itself.

I'm doing another dixie-cup test with iron powder, portland cement, fireclay & sand (no sal-ammoniac.) The latter three worked for foundries I built, iron powder could give it more heat resistance. Iron-silicate can withstand up to 3,000F.

Axismundi000
04-06-2013, 09:37 AM
I am full of admiration for this endeavour. Ostensibly it is to reduce cost. Making or modifying specific glassware as part of the process of Alchemy is a much more holistic approach where the Alchemist is more deeply involved in every facet of the Work.

thrival
04-08-2013, 01:10 AM
Axismundi000:

Thank you for the kind words, well I have to report the first try was a fail. I put the jar on the stove and was slowly cranking up the heat, I had steam coming out and bubbles forming on the bottom, thinking all was well, walked away and forgot about it. Came back to find the jar had broke, the coating got saturated and fell apart. That wasn't supposed to happen per the recipe, or my understanding it being a cold coating that didn't need to be fired, but hardened by chemical action between the iron & sal ammoniac. Guess I was wrong (hate when that happens! :p); Maybe I had too much other filler material. Why is alchemy so difficult! I'm just trying to make a rock! :D

So I did two more dixie-cups, one with iron powder, sand and portland cement, the other also included sal ammoniac. The first one seemed to get harder. So I mixed it up and coated another jar. At least using portland cement, once set, this one shouldn't fall apart when wet. But portland cement doesn't withstand heat for long. Losing internal water also causes loss of strength. But I'm hoping the silicates will bond with the iron as well as calcium in the cement. Those two metals have a electron potential difference and should cleave strongly. Well, I have my fingers crossed. Two layers is another possibility.

JDP
04-08-2013, 10:29 AM
Some comments:

1- Glauber did not invent anything new regarding this subject. Refractory coatings for glass and clay vessels appear in alchemical and chymical literature long before he was even born.

2- You are complicating it a bit too much. A simple mixture of clay and sand in several proportions will give you an adequate coating mixture. You can place the parts of the coated glass bottles and jars that contain the substances to be heated inside furnaces and heat them so hot that the glass actually melts within the "shell" of refractory material that is covering them, but the molten glass will be contained inside. I have tested this several times. I was able even to wholly decompose iron sulfate inside an ordinary green glass bottle coated by a mixture of 2 parts sand and 1 part clay. The half of the bottle that was inside the furnace melted into a "glob", trapping inside it the ferric oxide that formed during the decomposition of the sulfate (to get it back all that had to be done was to gently break the glass mass with a hammer.)

3- Even though it is not 100% necessary, it is advisable to first "cure" the coated bottles/jars by gently heating them on an electric plate or furnace, gradually increasing the heat to the point you can no longer touch the bottle/jar with your bare fingers. This helps remove moisture, "settle" and harden the mixture.

4- Even with the refractory coatings, it is always wise to gradually heat such bottles/jars. Never give them a sudden thermal shock. Refractory coatings are great, but not magical. The glass can still crack if given a strong heat too suddenly. These refractory coatings are ideal for heating the glass bottles/jars inside furnaces, where they can receive the increasing heat gradually, not for heating over a Bunsen burner.

5- I was even able to heat a coated ordinary glass bottle (one of those tall Lorina soda bottles) with a gas burner by first heating it gently over an electric hot plate, to the point that it could no longer be touched with the bare fingers, and then placing it above the gas burner. I was able to make the bottom of the glass glow, without any cracking. The bottle did finally develop some cracks after I turned off the gas burner, since it was cooling too rapidly, but by then you do not really care. The operation is technically over. You care about the bottle cracking while it is being heated, not after that. But heating in this manner requires patience and skill. Placing the room-temperature bottle directly over a gas burner will often result in cracking it, no matter how good your coating is.

Salazius
04-08-2013, 10:32 AM
Very nice, but you are forgetting a binding agent : fibers.
Cotton, lin fibers, as bands of tissue, wrapped around your jar, the whole thing saturated with your paste.

theFool
04-08-2013, 10:52 AM
One could wrap the glassware with aluminum foil, it can withstand direct heating from gas burner.

thrival
04-08-2013, 04:17 PM
Wow, thank you all!

JDP: I guess it's just a matter of asking the right question for the experts to come out! Well yes, technically I could put coated jars in my kiln, but I worry about the glass breaking, even at gradual temp change; and it sort of obviates what I thought Glauber was describing, i.e. a cold-cure coating that could be fired, but didn't necessarily need to be, to serve its dual purpose, i.e. strengthen/maintain glass integrity and contain corrosive liquids, should the vessel break (although he makes the reader think by using his "invention" the latter won't happen.) I want to use my equipment for many, many operations! ("Cant always get what you want"(?) I know there are cold-castable refractory formulas on the market if a person wants to go that route. The other thing I just realized is that coatings, fired or not, are going to react differently depending upon the corrosive acid they (might) be exposed to. For example, an iron chloride coating might not react to HCl but very well could be eaten up by nitric acid (or maybe the iron particles would weld together, which he describes as another of his invention elsewhere in his writings.) Apparently he never read Jabir because as far as chemical discoveries (nitre) he (Glauber) takes credit for quite a lot.

Salazius:

Are you suggesting I use Glauber's method of repairing glassware (linen soaked in egg, followed by quicklime powder cast on, followed by additional layers) pro-actively? ...and then the refractory? That could very well work! The problem I'm currently facing is once (unfired) clay gets moistened, containment is lost.

The Fool:

Aluminum foil will reflect heat, but won't contain acids very well. The purpose of the coating is to contain spills.

My current coating experiment (portland cement, sand/silica dust and iron powder) is curing in a bucket of dilute water-glass, but I'm beginning to see why industry relies on boro-silicates and fluorinated compounds.

JDP
04-08-2013, 11:10 PM
Wow, thank you all!

JDP: I guess it's just a matter of asking the right question for the experts to come out! Well yes, technically I could put coated jars in my kiln, but I worry about the glass breaking, even at gradual temp change; and it sort of obviates what I thought Glauber was describing, i.e. a cold-cure coating that could be fired, but didn't necessarily need to be, to serve its dual purpose, i.e. strengthen/maintain glass integrity and contain corrosive liquids, should the vessel break (although he makes the reader think by using his "invention" the latter won't happen.) I want to use my equipment for many, many operations! ("Cant always get what you want"(?) I know there are cold-castable refractory formulas on the market if a person wants to go that route. The other thing I just realized is that coatings, fired or not, are going to react differently depending upon the corrosive acid they (might) be exposed to. For example, an iron chloride coating might not react to HCl but very well could be eaten up by nitric acid (or maybe the iron particles would weld together, which he describes as another of his invention elsewhere in his writings.) Apparently he never read Jabir because as far as chemical discoveries (nitre) he (Glauber) takes credit for quite a lot.

For what you seem to want the glassware for you don't really need to bother with coatings. The refractory coatings are mostly for when you want to perform operations that require a strong heat, which would melt glass and some kinds of earthenware and make a mess in your furnace/kiln. For distilling liquids like acids, alcohols and the like you can either use your glass containers in a sand bath or directly on top of electric hot plates that can deliver the heat to the glass very gradually, like these electric plates from General Electric, which can be easily found in supermarkets:

http://www.walmart.com/ip/GE-Single-Burner-Hot-Plate/12442587

I have used all sorts of common glass bottles (sodas, Snapples, juices, beers, etc.) on these types of electric plates (directly on them, no sand bath needed), and only once did one of them crack (it had distilled vinegar attacking the bits of a litharge-soaked cupel that were stuck to the bottom of a silver piece), and that was after quite a bit of time of boiling the vinegar it contained. The heating plates you need to be careful with and that I do not recommend for heating common glass bottles/jars are the ones like this:

http://www.walmart.com/ip/Elite-Cuisine-Single-Burner-Hot-Plate/8467243?findingMethod=rr

The heating elements on these types of plates:

1- Do not heat as gradually as do the other kind (therefore they give more thermal shock to the glass)

2- Deliver a much stronger heat (they get red hot! enough so to melt lead on them)

However, you can actually heat common glass/jars on them IF you coat the bottom of the glass with a clay-sand mixture, as described above in my previous post, or place them in a sand bath.

thrival
04-08-2013, 11:33 PM
Dear JDP:

Thank you very much. I have a half-dozen hot-plates, heating elements and such, and have had several accidents, jars bursting when distillate back-flushed or jar too cold on a coil heating up. They were learning experiences but they taught me to plan for events I cannot forsee. If those jugs had contained hot acid the results could be catastrophic. I did learn to place shallow pans with a little sand on the hot elements to create separation from the glass and more evenly distribute heat, but I am still focused on containing ruptures if they occur. Accidents can still happen, even with all due care. Best to you.

Karl
04-09-2013, 02:17 AM
... A simple mixture of clay and sand in several proportions will give you an adequate coating mixture. You can place the parts of the coated glass bottles and jars that contain the substances to be heated inside furnaces and heat them so hot that the glass actually melts within the "shell" of refractory material that is covering them, but the molten glass will be contained inside. I have tested this several times. I was able even to wholly decompose iron sulfate inside an ordinary green glass bottle coated by a mixture of 2 parts sand and 1 part clay. The half of the bottle that was inside the furnace melted into a "glob", trapping inside it the ferric oxide that formed during the decomposition of the sulfate (to get it back all that had to be done was to gently break the glass mass with a hammer.)


Hi JDP-

Sintering the shell is a great idea. I'm curious about your proportions-are you doing a 20% high alumina clay mix with silica?

@Salazius- fiber is a good idea too. I bet fibreglass would be the thing in this application.

@Thrival- if cold coating continues to be appealing I would move to a mix of refractory cement, silica and fibreglass chop with a handful of perlite. I haven't tried that as a glass coating but it works as a furnace liner- the chop would help with cracking issues.

JDP
04-09-2013, 02:57 AM
Hi JDP-

Sintering the shell is a great idea. I'm curious about your proportions-are you doing a 20% high alumina clay mix with silica?

The one I usually use is a porcelain clay powder that does have a high alumina content (I forget the proportion of it), simply because I happen to have a few sacks full of it, so it's the clay I have most readily available at hand. Technically, though, any clay will work well when mixed with sand. Simple fireclays, ball clays, potter's clays, stoneware clays, etc. will do.

thrival
04-09-2013, 03:50 AM
Hi Karl;

Yes, fiberglass might be good, maybe with some potassium silicate as a binder, since it also tends to etch glass. My issue is I don't want to fire my glassware. I still like Glauber's linen, egg & quicklime recipe. it's primitive but hey, if it works... anyway for my current iron/silica/portland cement recipe, I have high hopes, as always, even before epic fails. :D

Update: this newer "cold" coating using portland cement instead of clay, mixed with iron powder, silica dust, and fine sand, has worked really well so far. It cured for a day in sodium silicate solution and is now hard as rock, very little porosity. After it has a chance to dry out I'll try a few drops of nitric acid to see how it holds up.




@Thrival- if cold coating continues to be appealing I would move to a mix of refractory cement, silica and fibreglass chop with a handful of perlite. I haven't tried that as a glass coating but it works as a furnace liner- the chop would help with cracking issues.

thrival
04-09-2013, 09:38 PM
I found this recently: http://www.corrosion-engineering.com/newsletterarticleshtml/TheAmazingAcidResistanceofPotassiumSilicateConcret e.html ...which discusses potassium silicate cements' resistance to nitric acid. ...also this: http://www.apexep.com/reactive-metal-heat-exchangers.htm (zirconium and titanium have good resistance to nitric acid; titanium oxide is a cheap paint ingredient) and lastly, http://www.cartech.com/techarticles.aspx?id=1670 (http://www.cartech.com/techarticles.aspx?id=1670) type 304 & 305 stainless steel resist nitric acid.

thrival
05-17-2013, 07:09 AM
I wanted to mention to others that my coating efforts have been a big FAIL. The problem is that, even using fiberglass tape as an underlayment, the coatings shrink and crack upon drying. Also plate glass has a fairly large coefficient of expansion that any coating would have to match. I tried Glauber's iron & ammonium chloride recipe, portland/sand and stainless steel powder, and even a geopolymer recipe that worked for kiln-ware. So far I have yet to find a cold-set material that doesn't need to be fired, with the same CoEf of Exp as bottle glass. I think I will just put the jar in a granite-ware stock-pot/sand-bath and call it done.