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Need help identifying glaze materials


MFP

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Thank you!  That's a big help!   I will be doing a cone 6 fire in the future with quite a few glaze samples on different bodies.....so this is perfect.  Yes two of the samples fizz vigorously with vinegar.  When I was last making glazes, we didn't use a wide range of materials.  I have identified two of the five at this point. One was zircopax (still going to test it) and the other was talc.  Of the remaining three, two fizzed with vinegar and one was inert.  This glaze recipe ought to make it very clear . Thank you!

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Very interesting chart.  Mark C did a test fire  and thinks substance #5 is Dolomite from the result of that fire. I don't think so because that sample was nonreactive with vinegar. The other two foamed vigorously. A new wrinkle is that when I put the 100 gram samples in little bowls for the loss on ignition test, I noticed that one of them was actually cream colored and tended to like to form into little loose balls. Later I was unpacking my new materials order when I noticed that the zinc oxide I was unpacking looked almost identical to the cream colored sample only a little more yellow but with the same tendency to clump into little loose balls.  Substances 1 and 3 reacted to vinegar. 5 did not and is somewhat gritty. The only other material that gritty was bone ash. I am going to make up a 100 gram sample of that glaze you gave me for #5. I had already made up the ones for 1 and 3.  If I didn't have about 50 pounds of #5, I would have given up by now. The only problem with the loss on ignition test is that there are quite a few substances which do not lose any weight during the firing.  After that I will get my husband to teach me how to use his propane torch and try the flame test. Thanks for all the information you have provided on this topic. Reading the different articles has been fascinating. Thank you! 

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It just said "zinc" on  the bag. The writing was nearly illegible  and things were spelled wrong...see what I mean about CAC? Also....good thing they package the way they do.....every single box was crushed but the bags inside were intact and inside there were plastic bags also....except if you got 20 pounds and then it was just a heavy duty brown bag. I think all the standing up and sitting down is what got my knee riled up.  It's better today....but another day chained to the chair. Then out of the blue my Mahavir feldspar showed up. I hadn't even checked the manifest yet. I had just finished getting things into containers and labeled and any excess labelled and put away. Yes I was wondering....my old zinc is white. Also....the talc was gross.....that's what you are using now?  Yuck.....oily looking grey stuff.....held it at arms' length when unpacking it. Fortunately, I bought wide mouth plastic containers....I could just trim the plastic bag, stick the tail in the jar and turn it over to have it run out into the container.....no dust. 

Going to visit Mark at Anacortes?  I went to that fair once. I was terrible at dealing with the public....at the end of the fair one of the shop owners on the street came and bought everything I had.  I never did well at those things.

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19 minutes ago, MFP said:

It just said "zinc" on  the bag. The writing was nearly illegible  and things were spelled wrong...see what I mean about CAC? Also....good thing they package the way they do.....every single box was crushed but the bags inside were intact and inside there were plastic bags also....except if you got 20 pounds and then it was just a heavy duty brown bag. I think all the standing up and sitting down is what got my knee riled up.  It's better today....but another day chained to the chair. Then out of the blue my Mahavir feldspar showed up. I hadn't even checked the manifest yet. I had just finished getting things into containers and labeled and any excess labelled and put away. Yes I was wondering....my old zinc is white. Also....the talc was gross.....that's what you are using now?  Yuck.....oily looking grey stuff.....held it at arms' length when unpacking it. Fortunately, I bought wide mouth plastic containers....I could just trim the plastic bag, stick the tail in the jar and turn it over to have it run out into the container.....no dust. 

Going to visit Mark at Anacortes?  I went to that fair once. I was terrible at dealing with the public....at the end of the fair one of the shop owners on the street came and bought everything I had.  I never did well at those things.

Yeah, heading up to Anacortes in a couple weeks to get myself a liscom hill original ;)

My talc is gray and slippery but not oily!  I think the white stuff is called french talc now?  Good news is local gray talc is cheaper than imported talc and just as magnesiumy.

I haven't dealt with CAC, they're a bit too far away for my taste, but SPS also bags inside of brown paper bags, but they're well marked with a stamp.

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It only looks oily. I figured out why the new talc will not work for Mark.  All the current stuff is ground soapstone. The talc he was using was pyrophyllite which is only mined in North Carolina. I told him to contact Laguna about getting some. The talc we got in the past were in layered sheets like shale or slate. The current talc is ground rocks. Apparently the difference is quite apparent under a microscope. 

I looked at SPS's site....they didn't have much of a selection of Laguna clays.  CAC also makes their own clays. I don't want to go through another round of experiments. I have decided on my cone 10 stoneware and porcelain....it's the cone 6 that is a problem....I have decided on a porcelain....it's the stoneware I am having trouble with. I really like the Welsh that CAC makes...it is the most similar to what I threw in the past. It also is not sticky....these new clays are so damn sticky that my fingers start grabbing 2/3 of the way up the cylinder wall.  

I think the shipping would be the same for either one for me.  My  knee is better tonight....bet my pots are all dried out  :(

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I am dealing with three unknown substances.  One of them is cream colored and has a tendency to form into loose little balls. I recently got a new materials order and the "zinc" was yellow and tended to form into little loose balls when I put it into the container.   I am used to zinc oxide being white. 

Of the three unknowns, Mark did a fire test and thought one was dolomite from the result of the fire, but I don't think so because that unknown sample was non=reactive with acid. It is slightly gritty and appears most similar to bone ash. So...the two which reacted to acid are either calcium carbonate or dolomite. All the other materials were accounted for.  I am going to do a loss on ignition test in the bisque on the three samples. Peter H also gave me a glaze recipe that would distinguish between dolomite or calcium carbonate in the glaze. So after Mark's result, I will make up that glaze with the third unknown. PeterH also sent me a link to a flame test method as well. 

If I didn't have 50 pounds of the one unknown I would have given up by now. 

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Stumbled across this oddity, ZnO changing colour when heated.

 

PS
The temperature dependence here  is because this is a  band-gap colour.

The causes of colour https://www.physics.utoronto.ca/~phy189h1/Causes of Color scientificamerican1080-124.pdf 

The origins of colour in minerals http://www.minsocam.org/msa/collectors_corner/arc/color.htm

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5 hours ago, MFP said:

Of the three unknowns, Mark did a fire test and thought one was dolomite from the result of the fire, but I don't think so because that unknown sample was non=reactive with acid. It is slightly gritty and appears most similar to bone ash. So...the two which reacted to acid are either calcium carbonate or dolomite.

I wondered if the combination of a weak acid and rather "rocky" mineral might mean that dolomite does not give a strong bubble test.

This reference seems to confirm some of these concerns:
The "Acid Test" for Carbonate Minerals and Carbonate Rocks https://geology.com/minerals/acid-test.shtml

Acid Reactions of Carbonate Minerals

Mineral Chemical Composition Cold Acid Reaction Warm Acid Reaction
Aragonite CaCO3 strong strong
Azurite Cu3(CO3)2(OH)2 yes strong
Calcite CaCO3 strong strong
Dolomite CaMg(CO3)2 weak yes
Magnesite MgCO3 very weak weak
Malachite Cu2CO3(OH)2 yes yes
Rhodochrosite MnCO3 weak yes
Siderite FeCO3 very weak weak
Smithsonite ZnCO3 weak yes
Strontianite SrCO3 yes yes
Witherite BaCO3 weak weak
Table 1: A list of commonly and occasionally encountered carbonate minerals with their chemical formula and reactions to cold and warm hydrochloric acid. Test results can vary because of weathering, previous testing, contamination, and specimen purity.

The effervescence using vinegar usually requires a hand lens for clear observation and is only observable with carbonate minerals that have a strong reaction with hydrochloric acid.


Maybe try leaving a small quantity in excess hot vinegar overnight? Even add a little detergent at the start and look for foam at the end??

Peter

PS Have you tried measuring LOI or specific gravity yet?

From digitalfire's list dolomite has a massive 46% LOI  (bone ash has zero). So well worth measuring LOI, only other high LOI's in the list
seem to be carbonates, alumina hydrate & cobalt oxide.

       
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Thank you Peter. You are always a wealth of information! 

For the purposes of clarity, let's refer to these unknowns as 1, 3, 5.  ( 2 and 4 got identified as talc and zircopax).    1 and 3 reacted vigorously with vinegar....I mean foaming. 5 was completely nonreactive and was slightly hydrophobic....leaving a thin film of dust on the surface when the vinegar was added. Obviously it is possible that 1 and 3 are both carbonates. Since I used a lot of celadon, one might be barium carbonate.....which does not lose any volume on ignition.  My knee has finally recovered to the point that I can get around again. I will try to upload pictures of these three rascals later today.  5 sure looks like bone ash.

(I did contact the supplier about that yellow zinc and Babs was right....calcined zinc.)

I was going to do the flame test after the ignition test since I am not doing a cone 10 fire until this winter. I have made up that glaze you gave me for 1 and 3 and will do one for 5 also for a cone 6 fire. If that doesn't answer the questions then I will try the flame test.  I was thinking of specific gravity but it's a huge pain in the butt. 

I am also suspicious that I have a whole can full of 5---that strongly implies that it was something I did not use that often---or I had just filled the can.  If I can ever find my glaze book, the answer may be in my Ohata Red recipe.....that glaze has the same gritty feel to it as 5 has and is probably in it.  The last big fire I did was an entire Ohata Red dinner set. 

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MFP-

All the various recipes that I have for Ohata Reds contain bone ash in varying amounts. You may be looking at bone ash, as any carbonate effects would be gone since it is already a fired material. Even if it is synthetic bone ash (tricalcium phosphate) it shouldn’t have a reaction to acid since it is a salt (residue from the interaction of acid with base), though I would expect that to be much finer in texture.

Hope this helps.

Regards,

Fred

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3 minutes ago, MFP said:

I was going to do the flame test ...

I was thinking of specific gravity but it's a huge pain in the butt.

I admire your persistence.

A video of some flame tests, which might give a better idea of what it actually looks like than "best still photos".

I'm not sure why you think measuring specific gravity is a huge pain in the butt. You may be right,
but theoretically it doesn't seem that difficult. For example:
- Take a measuring cylinder (cheapish on ebay etc) and part fill with water, then read volume.
- Add a given weight of powder, and read volume. 
- S.G. = weight/((density of water)x(difference in volume))

Never done it myself, but sounds pretty foolproof
- Measure volume from the bottom of the meniscus. e.g. https://www.911metallurgist.com/blog/how-to-read-a-burette
- Need fair quantity of powder for accuracy, and all should be below waterline.
- Requires the powder to be easily wettable with no air pockets.
- Maybe add a drop of wetting agent (d/w rinse aid or washing up liquid).
- Maybe do it twice to get an idea of the accuracy.

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Oh yeah, I just have graduated cylinders and distilled water laying around all over the place! I do however have a triple beam.  Like I said....if I didn't have 50 pounds of the stuff, I would have given up a long time ago!  Thanks for the video!  

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Thanks Fred!  The Ohata Red recipe I had used Kingman feldspar but it always had a gritty texture even with bentonite.  Since the last big fire I did was a whole dinner set glazed with Ohata Red....I am thinking I refilled that can. I also have compared it to materials I have and the only thing that gritty is bone ash. So I think we may be on to something. Since it is pre-fired as you point out, it should not lose volume on the ignition test.  My Ohata Red recipe was from 1973.  I still have some of the Ohata---looks like I used about all my five gallon bucket.....even though it is dried out now, probably only a gallon left. It was the one iron glaze I could identify because of the 10% iron and the grittiness....I actually found a glazed unfired pot that has weathered all the moves all these years!  Glazed with Ohata. 

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MFP-

Still thinking about what you said in your recent post, where you said:

”Thanks Fred! ….… My Ohata Red recipe was from 1973.  I still have some of the Ohata---looks like I used about all my five gallon bucket.....even though it is dried out now, probably only a gallon left. It was the one iron glaze I could identify because of the 10% iron and the grittiness....I actually found a glazed unfired pot that has weathered all the moves all these years!  Glazed withOhata. 

I think you may have a more accurate test for the material that might be bone ash. If you have access to a cone 10 firing, you could mix up your recipe with the unknown in place of the bone ash apply it to a test piece and fire it next to the unfired piece and another test piece with your left over Ohata glaze. Even if some of the other materials have changed, you should have some real comparisons after firing the.

Just a thought.

Regards,

Fred

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Thanks, Fred. The one thing I have not yet found is my glaze book, but I got an Ohata recipe courtesy of Bill off glazy that looks right. I am not going to do cone 10 fires until this winter.  I have never fired this 2831 before and have not idea how much heat I am going to be dealing with.....so I want to be able to open the shop door and have the winter suck all the heat out (I am in Idaho). I don't want to install a vent.  I will try your suggestion of making an Ohata glaze with that #5 and see what happens. I am going to be really interested  in the loss on ignition test. I bet it doesn't lose any. I have learned so many new things on here. It's been really neat. Thanks again for your good suggestion.

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On 7/22/2019 at 11:00 AM, PeterH said:

I admire your persistence.

A video of some flame tests, which might give a better idea of what it actually looks like than "best still photos".

I'm not sure why you think measuring specific gravity is a huge pain in the butt. You may be right,
but theoretically it doesn't seem that difficult. For example:
- Take a measuring cylinder (cheapish on ebay etc) and part fill with water, then read volume.
- Add a given weight of powder, and read volume. 
- S.G. = weight/((density of water)x(difference in volume))

Never done it myself, but sounds pretty foolproof
- Measure volume from the bottom of the meniscus. e.g. https://www.911metallurgist.com/blog/how-to-read-a-burette
- Need fair quantity of powder for accuracy, and all should be below waterline.
- Requires the powder to be easily wettable with no air pockets.
- Maybe add a drop of wetting agent (d/w rinse aid or washing up liquid).
- Maybe do it twice to get an idea of the accuracy.

Well....the results are in on the loss of ignition test.  #1 looked slightly burnt and lost 53 grams. #3 fused together and loss NO weight.  #5 turned pink and lost 53 grams. #3 fusing and leaving little green spots was totally in expect.

#3 LOI result.jpg

#1 LOI result.jpg

#5 LOI test result.jpg

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14 hours ago, MFP said:

Well....the results are in on the loss of ignition test.  #1 looked slightly burnt and lost 53 grams. #3 fused together and loss NO weight.  #5 turned pink and lost 53 grams. #3 fusing and leaving little green spots was totally in expect.

What conclusions are you reaching? I can see #1 & #3 fitting in with your ideas of carbonates. However #5 at 53% LOI looks "interesting/surprising".

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I am thinking that #3 is barium carbonate. Unlike calcium carbonate, it loses no weight/mass on ignition. That means that 1 and 5 are likely calcium carbonate and dolomite respectively. I have made up that glaze you provided with all three.  I cannot think of any other material that I used in those days which would fuse on ignition like that. I used a lot of barium carbonate.  If it was a feldspar or silica, it would just sit there.   What are your thoughts?

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Were you buying Barium Carb in such quantities...just asking as one would prob not buy huge amounts of such a toxic product and not label it...but back in the day....maybe.

If firing to c 6 then use it in a test quantity of glaze you know as barium glaze and same glaze mix it as bone ash and see:-(

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