Marcia Selsor Posted July 19, 2016 Report Share Posted July 19, 2016 Time to make some new saggars. I asked Ron Roy about this. He doesn't have a clue.'t happens to my spare raku buttons sitting in my studio and to a few other things. Not sure what is in the air. I had to replace the castors on my pug mill and some on a ware cart because the rubber coating cracked off. Link to comment Share on other sites More sharing options...
glazenerd Posted July 19, 2016 Report Share Posted July 19, 2016 Do you have pyrophyllite in these? and or CC clay? Nerd Link to comment Share on other sites More sharing options...
Marcia Selsor Posted July 19, 2016 Author Report Share Posted July 19, 2016 Time to remake saggars. Only a few of them do this, but they've been doing this since I lived here...even before foil saggar firing. It also has happened to the same clay I made raku kiln buttons. I found a few in my studio doing this flaking. This is not due to firing. I asked Ron Roy and sent him photos. Also talked to him at NCECA a few years ago about this. No clue. Hopefully my raku clay will be more resistant. Things rot down here...like the rubber on the casters of my pug mill or shopping bags and the nylon on my husbands golf bag. Link to comment Share on other sites More sharing options...
Magnolia Mud Research Posted July 19, 2016 Report Share Posted July 19, 2016 Marcia, Speculation ! [i am assuming the saggar is a bisqued fired clay body made with more refractory clay than your regular clay body] The saggars are delaminating from exposure to high moisture levels and partial rehydration of the fired structure followed by refiring. The expansion contractions of the firing cycle along with the buildup of deposited salts in the pores lead to small cracks growing into bigger cracks. The salts react with the saggar at firing temperature forming new - but different - material that helps to keep the cracks to grow. The photo resembles the worn refractory inside a coal gasification pilot plant reactor that cycled up and down every week for several years. LT Link to comment Share on other sites More sharing options...
glazenerd Posted July 19, 2016 Report Share Posted July 19, 2016 This thread posted twice, so my question showed up in the other one. I worked on a 50/50 text blend switching out some silica for pyrophyllite: it scaled badly. Not saying this is the problem, but that flaky goodness reminds me of it. Nerd Link to comment Share on other sites More sharing options...
Marcia Selsor Posted July 20, 2016 Author Report Share Posted July 20, 2016 Double post...I asked John to delete it. but that doesn't explain the bisqued only buttons in my studio doing the same thing. I suspect something in this specific clay body, something is responding to some toxics ingredients in the environment. I had a pair of shoes in my closet for some time. I worn them after a year or two of no use. They disintegrated as I walked in them. I think it is environmental. But something in one specific clay body. Unfortunately I don't know which one it is. I have used several raku bodies since I moved down here. Armadillo in Austin, Clay World in San Antonio, and Ceramic Store, Inc in Huston, and Alligator Clay in Baton Rouge. I worry that is something from Matamoros crossing the border. I worry that it is doing something worse to our bodies. Marcia Link to comment Share on other sites More sharing options...
jrgpots Posted July 20, 2016 Report Share Posted July 20, 2016 Marcia, Do you have a special recipe or secrets for making your saggars? I'm all ears... I was just thinking aloud.... 1. Do you think adding kyenite might prolong them? 2. Can you coat the inside of the saggar with ITC100 (or similar product) to make the internal wall less porous to soda and volotile gasses? 3. How many firing do you get from your saggars, anyway? I ask because i'd love to make some. Jed Link to comment Share on other sites More sharing options...
Marcia Selsor Posted July 20, 2016 Author Report Share Posted July 20, 2016 Jog, I neve had this problem until living in S. Texas across the border from the matamoros dump with constant burning. I have used Kyanite in my raku clay bodies. I have just been using my raku clays. I have always used my raku clay for about 20 years. I can get many firing out of some, maybe 1/2 dz out of short-lived ones and many more out of others. I retire many pieces until I like the results.This does not seem to be a result of firing since the same corrosion happens to my raku clay buttons in my studio txt have not been fired after one bisque. I think it is something in the air. I had planters in Montana that corroded in a similar scaly fashion with the water from my house. High nitrates. Marcia Link to comment Share on other sites More sharing options...
glazenerd Posted July 20, 2016 Report Share Posted July 20, 2016 Marcia: I am not a chemist, but in my recent relearning, acid would be the prime suspect that would eat both organic and inorganic. Although potassium is used to tan leather, and high levels will make a clay body flake. You have something else in your area besides the dump burning. Across the border from Brownsville is the Zinc Nationale zinc plant in Mexico. They use a rotary kiln to burn off the impurities in zinc: does the wind blow from that direction? Nerd Link to comment Share on other sites More sharing options...
Magnolia Mud Research Posted July 20, 2016 Report Share Posted July 20, 2016 Marcia, Nerd: From what you have said about sources of air pollution, I suspect sulfur and nitrogen oxides (SOx/NOx) from incinerators are part of the decay mechanism. I also suspect that the salts from the ocean spray may have a subtle contribution, especially combined with high sulfur and nitrogen oxides from incinerators and the calcining industry. The ocean spray solids are sub-micron crystals of sea salt and misc "stuff" dissolved in sea water. The SOx/NOx adsorb onto surfaces and inside pores and may react to produce sulfates and nitrate salts, especially sodium, potassium, and calcium salts. These salts will slowly hydrate from moisture in the air and results in the growth of the deposits and can propagate the cracks. More cracks expose more surfaces to adsorb more .... And things eventually fall apart. The salts when dissolved in water are more acidic than pure water and this may also add to the decay beyond just crack growth. The decaying ceramic objects have in common high open porosity, firing to temperatures significantly lower than their vitrification points, and exposure to the likely adverse environmental conditions. SOx/NOx will degrade the polymers (rubber, etc) used in shoe soles and casters. I have observed in some old flower pots the delamination decay you described and showed in the photos here in the Houston area. The pots were just sitting in the weeds for more than several years getting wet/dry with rain, yard sprinklers and varying amounts of garden leaf mold. When we moved them, the pots fell apart. Since the mechanism I have described is basically a property of the porosity of the failing objects, sealing the surfaces to environmental exposure may be a mitigation option, but not likely to be practical for saggars. But storage in an controlled environment perhaps is worth considering. Marcia, Have you compared / contrasted the decay of the saggars to the response to pieces of your Raku work to environmental conditions? Look for conditions that are alike and different and the response to those conditions. That is what I would do if I were still doing what I used to do. The explanation of the phenomena you observe would be a good MFA project for an bright rising star at your favorite university arts and sciences department and might even be a good NCECA or ACerS MST presentation. LT Link to comment Share on other sites More sharing options...
Marcia Selsor Posted July 21, 2016 Author Report Share Posted July 21, 2016 what is CC clay? No pyrophylite. It is commercial raku clay. I brought some with me from Montana 10 years ago (left from an order of 4000 lbs) and have purchased several types since then. Some is from San Antonio, some from Armadillo, some from Alligator clay. So I am not sure which clay is doing this. Pretty weird, isn't it. That flaking happens sitting around my kiln shed. This morning I unloaded my little test kiln and the bottom bacd on the bottom floor section of the kiln feel off. The welds on the hose clamps rotted. There was more rust on the inside of the band than the outside. The main casing around the main body is going and at least one of the hose clamps hate snapped lose. Marcia Link to comment Share on other sites More sharing options...
Magnolia Mud Research Posted July 21, 2016 Report Share Posted July 21, 2016 Marcia, In Brownsville, you will be subjected to a nontrivial amount of suspended sea salt dust in the air that comes from the Gulf of Mexico. The dust has a particle size smaller than you can see and with a settling velocity nearly zero. These particles, when heated above about 500 C, will begin to react with the air moisture to produce a nontrivial amount of HCl vapor. The HCl vapor reacts with the air moisture as the air cools and will form tiny droplets of muriatic acid that will corrode the surfaces they collide with or settle on. The further away from the sea the less salt there is in the air. I am about 70 miles from the Gulf, and it is not serious here. This may also contribute to the delamination of your saggars. Without a heat source to convert the salt to acid vapors, the corrosion is just that from salt exposure. On a kiln during the startup and shutdown sequences, the outer surfaces will be where the acid corrosion are more likely as they are the last to be heated and the first to be cooled. The amounts of acid produced are a very small fraction of the salt and will be limited by the low levels of moisture in an electric kiln environment, but for a combustion kiln the moisture level from will be large enough that the salt concentration and temperature levels will be the limiting variables. LT Link to comment Share on other sites More sharing options...
Marcia Selsor Posted July 22, 2016 Author Report Share Posted July 22, 2016 I think it is much more than any firing temperature and Gulf salt. Why does this happen to raku buttons I made years ago when they are sitting inside my studio, not the kiln room. Why does this happen to rubber casters or heels of shoes in my closet? Golf bags in the garage? Try Matamoros dump. Also Yucatan smoke. Something is very toxic down here beyond the Gulf sea corrosion. Thanks anyway. I can set a utility knife out overnight and it is rusty in the morning.We are 25 miles from the coast. We are 2 miles from Matamoros and the dump is burning constantly. Marcia Link to comment Share on other sites More sharing options...
Babs Posted July 27, 2016 Report Share Posted July 27, 2016 Time to go to wild Montana😊 Link to comment Share on other sites More sharing options...
Marcia Selsor Posted July 30, 2016 Author Report Share Posted July 30, 2016 Leaving Thursady to go house hunting. Have five set up to see. Very excited. Marcia Link to comment Share on other sites More sharing options...
glazenerd Posted July 30, 2016 Report Share Posted July 30, 2016 Marcia: Happy hunting, may your dreams come true. When you get settled in, perhaps you can find me some wilimete samples? Nerd Link to comment Share on other sites More sharing options...
Marcia Selsor Posted July 30, 2016 Author Report Share Posted July 30, 2016 Going to Montana to continue house hunting. Bet here by next weekend. We can't wait. Link to comment Share on other sites More sharing options...
Marcia Selsor Posted July 30, 2016 Author Report Share Posted July 30, 2016 Going to Montana to continue house hunting. Bet here by next weekend. We can't wait. Link to comment Share on other sites More sharing options...
Marcia Selsor Posted July 30, 2016 Author Report Share Posted July 30, 2016 Great idea. I have not notices and problems with any finished pieces. The saggars were made from commercial Raku clay from various sources. NOt sure if it is one brand. I will try to document that. NOt all the raku buttons dissolved. Just a couple sitting in my studio. Others are ok in a plastic bag. Link to comment Share on other sites More sharing options...
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