Jump to content

MFP

Members
  • Content Count

    291
  • Joined

  • Last visited

Everything posted by MFP

  1. Thank you! Who sells that please?
  2. Thank you very much Neil.....exactly what I was looking for.
  3. Yes....although "talc" is a homogeneous term in pottery meaning "stearite", it is a heterogeneous term in mining....referring to at least 8 different minerals depending on the application. Pottery was even less of a market share 30 years ago than it is now.....there's no telling what we got when we were using "talc". I know we had to abandon at least two glazes because one of the materials that showed up were no longer the same....and we couldn't get what we had previously. I am sure the university was using soapstone....but other people were using whatever people said "talc" was....glaze theory and glaze calculation was not the norm in the pottery community.....you had recipes and you followed them....if a material changed....you just did not have that glaze any more. Thankfully, times have changed.
  4. This was my point.....that pyrophyllite is marketed as talc because of its physical properties, not its chemical properties. Layered talc often was in alternating layers of talc and pyrophyllite. And I agree.....that the name was not in any way related to the contents. What I highly suspect was that the talc we got was from a layered deposit contaminated with Dolomite, pyrophyllite, and Wallosanite. However, since my friend has tried all the current magnesium containing talcs.....it didn't hurt to give pyrophyllite a test---just in case that is the "talc" we got 35 years ago--- since these marketers only care about the physical properties in most cases (for example.....one mineral they call "talc" is almost entirely asbestos).. When you look at pyrophyllite and touch it, you could not tell the difference from true talc.
  5. After what I have discovered about the variability of talc deposits and all the different minerals being sold as talc.....I would not be surprised at all,,,,especially considering that the ceramics community was 1% of their market....and physical properties were what they were after, not chemical properties---which don't seem to concern them at all.. Bottom line....pyrophyllite is considered a talc....not the talc we use in the pottery community....but it is used in other ceramic applications. And like I said....Mark is not out anything to try it in that glaze recipe. I know when I am doing tests of my old glaze recipes, I am going to one of each....because this ugly grey stuff is nothing like what we used to use. I sent what 30 year old talc I had to Mark already, but I only had a couple of pounds left. I had not seen this stearite stuff at that time. I can tell you.....it is not the same as what I used in the past. If pyrophyllite isn't what it was.....we are both screwed in terms of our old recipes. Since Mark had already told me that all the current ones did not work......it was clear that magnesium might be the issue.....and pyrophyllite has hardly any. So...if this "talc" doesn't solve his problem with that one glaze....I have no further suggestions--- as it is clear that the chemical properties change from mine to mine and within the same mine on any given day. I got a lot of info from the US Geological service. That's how I found the North Carolina mines.
  6. PS---what I also discovered is that although we are interested in the chemical properties of talc.....the people mining it are much more interested in its physical properties. The reason they call pyrophyllite a talc is because their physical properties are very similar. I can tell you in handling this powder that it acts exactly like talc....sticks to your fingers etc. Sorry....the digitalfire is not consistent with what I have previously found. I am not going to argue about this any more. I was trying to help Mark out. Since I bought the pyrophillite....he is not out anything to make a 100 gram batch to test it for his one glaze. I am also talking about chemicals that existed 35 years ago.....and things were much different then.
  7. Thank you.....yes that is what I am trying to duplicate. What I meant...sorry I was not clear....is can you mix a stain with water and use it like an oxide on bisqueware.....and is this what he is doing here? Or is it being added to a thin slip and then applied. I am thinking that Mason best black. There was also a stain in the "adding colorants " manual here on the site. But it looked pretty complicated and had to be milled for hours and I do not have a mill.
  8. Did you see the above grid that says Pyrophyllite-Talc group? What I am thinking is that we were sold "desert talc" that was pyrophyllite which is why it is so different in the glazes calling for it==because it doesn't have magnesium. . I am NOT suggesting it is true talc. I bought this from Ceramic Supply in Pittsburgh.....so someone is using it for something. If it doesn't work for Mark...then it has simply been ruled out. He said something about Texas talc kind of working and that was where pyrophiyllite was being mined before that mine shut down. Before that was the Mojave desert. Now only in North Carolina. I have put hours of research into what "desert talc" was......and discovered it wasn't really talc at all but the industry calls it that. So..it is simply an option for Mark to try, If it doesn't work....then some other kind of screwy talc is the reason. IN researching this, I found that the talc is often mixed with other veins of minerals like Wallosanite, Dolomite, and calcium deposits. So....if the "desert talc" he was getting was contaminated with a particular blend of talc, Wallosanite and Dolomite....we will never be able to duplicate it.....and would account for the difference as the amount of magnesium would be much reduced. I actually talked to the mine in Montana.....and every day there is a different type of soapstone coming out of the mine. It changes constantly. And they don't do any assays to determine its composition ongoing. So literally, the talc can vary from batch to batch.
  9. There are far more forms of talc than are used in pottery.....and it is possible that over the years, depending on which mines were operating.....people got sold "talc" of all kinds...not very helpful when trying to replicate old recipes and vendors have used this generic term for what are distinctly different minerals. The stearite group is what we are using now as "talc". Varieties of TalcHide Beaconite A fibrous variety of talc resembling asbestos. Chromian Talc A Cr-bearing variety of talc. Polyphant Stone A greyish-green potstone flecked with whiteand brown. Used since Norman times as an ornamental stone in churches. Pseudolite Octahedral talc pseudomorphs after spinel. Steatite A massive variety of talc with a greasy feeling, often used for ornamental carvings. Zincian Talc Zn-bearing variety from the "Mixed Series" formation, Nežilovo, Macedonia. Associates, i.a., with ferricoronadite. Relationship of Talc to other SpeciesHide Member of: Pyrophyllite-Talc Group Other Members of this group: Ferripyrophyllite Fe3+Si2O5(OH) Mon. Minnesotaite Fe2+3Si4O10(OH)2 Tric. 1 : P1 Pyrophyllite Al2Si4O10(OH)2 Tric. 1 Willemseite Ni3Si4O10(OH)2 Mon. Common Associates
  10. Since it has minimal magnesium that may be the difference...and it has more alumina. But....I don't know why it is in the talc category, especially since now magnesium is expected in talc. But I know 30 years ago..."desert talc" was what was used.
  11. You are missing the point completely. What I found is what used to be called "desert talc" and was called for in old recipes was identical to pyrophyllte and was NOT stearite,,,,aka soapstone....and is why old recipes that call for "desert talc" do not work with stearite because of the magnesium content. I didn't name it that....someone else did. It is not a rock like soapstone and is deposited in layers like shale. So we will see if it replaces the misnamed desert talc in Mark's recipes....and it is likely to be what I will need in my old recipes. Here are the four types of talc.....number three is the pyrophyllite group. What is used now is the stearite/magnesium group. In the past, it was different,. There are four types of talc deposits: Deriving from magnesium carbonates. ... Deriving from serpentines. ... Deriving from alumino-silicate rocks. ... Deriving from magnesium sedimentary deposits. The type called desert talc is only 10 percent of all talc produced....most likely because it is SO different from the others.
  12. Maybe in CURRENT recipes....but I am talking about people who are having trouble with OLD recipes because this new talc has those impurities in it. OLD recipes rely on the OLD talc. This talc is used for a different purpose. PYROPHYLLITE PYRAX® B Pyrophyllite is used in rapid-fire ceramic wall tile bodies. It lowers firing temperature; produces low moisture expansion bodies with good craze resistance; increases thermal shock resistance; and greatly increases firing strength in vitreous bodies. PYRAX B promotes the development of mullite when substituted for an equivalent amount of feldspar or quartz. PYRAX ABB Pyrophyllite is generally used for the same applications as PYRAX B, but it shows wider variations in mineralogy and particle size distribution. PYRAX RG refractory grade pyrophyllite is used in refractory mold washes insulating firebrick, metal pouring refractories, alumina-silica monolithic refractories, ramming mixes, gunning mixes, castable mixes and kiln car refractories. Al2O3 17% 21% 0. 7% 38% 36% SiO2 77% 72% 50% 45% 46% Fe2O3 0.4% 1.9% 0. 2% 1.0% 1.7% TiO2 0.2% 0.5% < 0. 1% 1.5% 1.4% CaO <0.1% 0.1% 45% <01% <0.% MgO <0.1% 0.1% 1.5% 0.2% <0.1% Na2O 0.2% 0.4% < 0.1% <01% <01% K2O 1.2% 0.3% < 0.1% 0.5% 0.4% LOI 3.6% 4.0% 1.6% 14% 14% For technical questions regarding these products or their use in your application, please contact our R&D center at MineralLab@vanderbiltminerals.com or click on the Technical Inquiry link on any www.vanderbiltminerals.com website page.
  13. Two different minerals with similar physical properties are talc and pyrophyllite. Their physical properties are nearly identical. Both are very soft: talc is the softest mineral on the Moh's hardness scale at 1, and pyrophyllite is 1 to 2.Both talc and pyrophyllite have perfect cleavage in one direction. This means that these minerals break into thin sheets. As a result, both feel greasy to the touch (which is why talc is used as a lubricant). They are both formed in metamorphic environments as the result of changes in silica-rich dolomite. Steatite and soapstone are impure, massive forms of talc that lack the distinctive cleavage mentioned above." These are the forms that are currently being sold to Laguna. This is not the same as pyrophyllite. So maybe talk to the Laguna guy about getting some North Carolina talc. The chemical formula for the pyrophyllite is : Al2Si4O10(OH)2
  14. Thank you both, I should have been more clear....the vase was not in the video. The box is lined with a green celadon. Somehow that video has changed....it used to look black and white on the lid...not a darker green breaking on the texture. I did see him make it....it is very white porcelain even when wet. And it was slab rolled and applied. Any idea what the red glaze is? He uses it a lot...I am thinking a clear with Mason 6003
  15. So...black and white underglaze stripes with a clear over the top....it didn't have that look but I will try it....it almost looked like black and white glazes side by side....but there was no blending of the two together. Can you use a stain like an oxide if you have the right glaze? There was another pot he used it on where he had clearly drawn lines over a glaze that were black,,,but again no blurring or running. I wish I could copy it and post it. Here is the url.....it is the lid of the box. He had a vase where it was vertical stripes on the neck. https://www.youtube.com/watch?v=3tcbcO_vwdQ&t=24s It is right at the beginning of the video....sometimes for some reason....it gets cut out. There is another brown box....it's not that one.
  16. I recently saw a pot with vertical black and white stripes up the sides......the black was a pure black....no blurring, no running, crisp edges. . Anyone have any idea how this is achieved? It was a white glaze. I was wondering if it was black stain applied to the surface. Any ideas would me most appreciated.
  17. I discovered in my hunt to try to figure out why Mark needed old talc for some of his recipes, that what we used to call desert talc was a substance that was deposited in layers like shale....and that there were two almost identical forms,.....the desert talc and pyrophillte. The talc we are getting now is literally ground soapstone and is not even the same as desert talc. Apparently if you look at the two under a microscope the difference is readily apparent. I then discovered that it is mined in North Carolina and is markedted as Pyrax by the same company that makes Vansil Wallosanite feldspar. Ceramic Supply in Pittsburgh carries it. I got ten pounds....and yes....it is beautiful white fluffy talc. I am sending some to Mark to see if it in fact works in his old recipes. I am also suspicious that I will need it for my old cone 10 recipes as well. So....this post is just an FYI for anyone having problems with the new talc. This is an alternative to try.
  18. Yes...add enough gerstley borate to a glaze and it will bleed.....and run....all over the place.
  19. Yikes! But to be totally honest, there are just bodies I like more. Everyone is different which is great....imagine the problems if we all liked exactly the same things!
  20. The senior moments just keep coming more and more frequently! I think we talked about S cracks or was that Neil?
  21. Thank you! I will take a look!
  22. Actually, after a discussion with Min.....I am less concerned about this. It was more force of habit I suppose since stoneware was the norm when I was last working and workable porcelain was fairly non-existent. I have actually found the new porcelains to be easier to work with than these new stonewares. I don't care for Bmix.....although it takes glazes well, I find it has all the disadvantages of porcelain and none of the advantages. Min noted more problem with S cracks with these stonewares and that has also been my experience. I found a stoneware body from Clay Art Center.....a cone 6 and 10 versions that are for larger pieces and ovenware. So, if I need a stoneware, that is what I will use. After this first test fire, I see clearly that porcelain is not "delicate". The New Zealand porcelain from Clay Art Center is whiter than Frost and you could bludgeon someone to death with it.....it would take a lot to break it. So I think I have finally figured out what I am going to use for what.
  23. http://www.greatkilns.com/resources/operating-manuals.html This is all the manuals available: It is in the electric kiln one. If you click on any of the below, it takes you right to the pdf. Kiln Sitter Manual LT3K Kiln Sitter Manual P&K 3 Key Manual RTC-1000 Control Manual Electric Kilns Operating Manual Standard 3 Key Cone Fire Manual Orton Auto-Cone Manual Orton VentMaster Manual V6CF Manual V6CF 700 Series Olympic Gas Kilns Manual High Limit Controller for Gas Kilns Manual Gas Blower Burner Glass & Heat Treating Kilns Manual Genesis Manual
  24. Got it downloaded...but this site does not upload pdf files It also won't copy and paste. I don't have the conversion program. You can download the entire manual directing from the Olympic site. It is on page 56 of the trouble shooting section. They just have one generic manual for all their kiln.
  25. I don't mind sharing at all. The entire manual is too large to upload....I already tried. I am trying to figure out how to save this single page to my desktop so I can just upload that
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.