MFP Posted August 3, 2019 Report Share Posted August 3, 2019 Are magnesite magnesium carbonate the same? Can they be interchanged? Link to comment Share on other sites More sharing options...
liambesaw Posted August 3, 2019 Report Share Posted August 3, 2019 4 minutes ago, MFP said: Are magnesite magnesium carbonate the same? Can they be interchanged? One is the mineral (magnesite), and then other is the chemical (magnesium carbonate). The difference being that one is raw and the other refined. If magnesium is what you're after either should work, but if pure magnesium is what you're after the carbonate should be used. Magnesite can have impurities like iron, nickel, etc. The comparison would be something like Rutile and titanium dioxide. Technically Rutile is titanium dioxide with impurities. Titanium dioxide fires an opaque white, and Rutile fires to an opaque yellow. You can expect similar variation between magnesite and magnesium carbonate. Link to comment Share on other sites More sharing options...
MFP Posted August 3, 2019 Author Report Share Posted August 3, 2019 So if a recipe calls for magnesite, how much MgCO3 do you use? Link to comment Share on other sites More sharing options...
liambesaw Posted August 3, 2019 Report Share Posted August 3, 2019 I think they're probably equal besides the trace minerals. Might want to pop it into digitalfire to make sure Link to comment Share on other sites More sharing options...
Babs Posted August 3, 2019 Report Share Posted August 3, 2019 I think magnesite is magnesium Carbonate... MgCO3 I've had recipes which have called for the heavy one but too far in the past to think out why.. Light Magn.Carb is a bit different. Hydrated MgCO3 Link to comment Share on other sites More sharing options...
MFP Posted August 4, 2019 Author Report Share Posted August 4, 2019 Well I went to digitalfire as Liam suggested and it does not differentiate between them. I was wondering how to adjust a recipe if it called for magnesite....clearly putting too much mag carb will cause crawling. Link to comment Share on other sites More sharing options...
Min Posted August 4, 2019 Report Share Posted August 4, 2019 Magnesite is 47.8% MgO and Light Magnesium Carbonate is 43.09% MgO. So, if for a hypothetical example, a glaze has 5% magnesite in it and you use magnesium carb in place of it you are only going to be short by the difference between the two which is 4.7% multiplied by the 5% in the glaze which works out to 0.235 grams. It's really a negligible amount. I don't think it makes a difference if you use Magnesite, Magnesium Carbonate or Light Magnesium Carbonate when working with the typical amounts found in glaze recipes. If you're using the Magnesite or Magnesium Carbonate only to supply magnesium there are better ways to do it. (exception being crawl / lichen glazes) Talc to supply the magnesium content has a far lower LOI therefore far less issues with crawling or pinholes. This is where glaze calculation software is really helpful, post your recipe if you like and someone can likely convert it for you if you're interested. Link to comment Share on other sites More sharing options...
MFP Posted August 4, 2019 Author Report Share Posted August 4, 2019 Thank you very much Min. You are always so very helpful. I saw some glazes on glazy with magnesite in the recipe and I had never heard of it. I have to get with it and study that calculation formula Bill gave me. I am trying to focus on cone 6 now since I made the decision that cone 10 is a winter enterprise. I think I have found a stoneware I like and at least two porcelains. So, I have been getting things together for the first glaze test fire. There are so many choices on glazy it is difficult to decide. However, I want one that is like the white matte I had....it was white and somewhat buttery when thick and when thin it was reddish.....it was nice for pots with texture. I think I found one on glazy for cone 6. Thanks again for the information.....if I am understanding magnesium, less is better unless crawling is desired. Link to comment Share on other sites More sharing options...
Min Posted August 4, 2019 Report Share Posted August 4, 2019 "less is better unless crawling is desired." It's the material that supplies the magnesium thats the issue with crawling and pinholes not the magnesium oxide that will be in the fired glaze. High magnesium glazes can be wonderful, just suggesting to supply the magnesium content with talc (or dolomite if there is calcium in the recipe, many do) or a combination of those two materials instead of magnesium carb or magnesite. I use low expansion glazes and many include a fair bit of magnesium from talc, dolomite and a frit, crawling is never an issue. Link to comment Share on other sites More sharing options...
liambesaw Posted August 4, 2019 Report Share Posted August 4, 2019 10 minutes ago, MFP said: Thank you very much Min. You are always so very helpful. I saw some glazes on glazy with magnesite in the recipe and I had never heard of it. I have to get with it and study that calculation formula Bill gave me. I am trying to focus on cone 6 now since I made the decision that cone 10 is a winter enterprise. I think I have found a stoneware I like and at least two porcelains. So, I have been getting things together for the first glaze test fire. There are so many choices on glazy it is difficult to decide. However, I want one that is like the white matte I had....it was white and somewhat buttery when thick and when thin it was reddish.....it was nice for pots with texture. I think I found one on glazy for cone 6. Thanks again for the information.....if I am understanding magnesium, less is better unless crawling is desired. If you've got some disposable income the "cream breaking rust" glazes are similar to what you're describing. They've got a lot of tin in them though and other opacifiers don't work as substitutes. Link to comment Share on other sites More sharing options...
liambesaw Posted August 4, 2019 Report Share Posted August 4, 2019 4 minutes ago, Min said: "less is better unless crawling is desired." It's the material that supplies the magnesium thats the issue with crawling and pinholes not the magnesium oxide that will be in the fired glaze. High magnesium glazes can be wonderful, just suggesting to supply the magnesium content with talc (or dolomite if there is calcium in the recipe, many do) or a combination of those two materials instead of magnesium carb or magnesite. I use low expansion glazes and many include a fair bit of magnesium from talc, dolomite and a frit, crawling is never an issue. Yep, it's that +50% carbonate loss that causes the crawling. If you follow Tony Hansens doctrine at all he aims to eliminate as many lossy ingredients as possible. This means loss on firing and loss from solubles. Both cause issues in otherwise chemically good glazes. Link to comment Share on other sites More sharing options...
MFP Posted August 4, 2019 Author Report Share Posted August 4, 2019 Thank you Min.. Hopefully soon this will all start making more sense to me. I just have to put in the time. Link to comment Share on other sites More sharing options...
MFP Posted August 4, 2019 Author Report Share Posted August 4, 2019 Disposable income? Yes, there was exactly that glaze on glazy.....the only one I found. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.