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Posts posted by JRW

  1. Hi Rew and everyone,


    I appreciate this thread, and I stumbled upon it because I am in the middle of my own freakout about silica dust. I have been doing pottery for 2.5 years and have been pretty blase about dust. I have done a lot of dry sanding of greenware (outside), and have worn an N95 mask for most of it. Since COVID, I learned that N95 masks do not work well for people with beards like myself, and so now I am quite concerned that all that time I was breathing in massive amounts of silica. I am having some lung irritation and phlegm production that is making me paranoid. Does anyone know if wearing an N95 mask with a beard offers ANY protection? Or was I basically just breathing in dust all that time? I can't seem to find much information about this online other than the generic "there must be a tight seal" warning. If there isn't a tight seal is the mask completely useless? Thanks...

  2. Hi All,


    I am mixing Mason Stains into Laguna s-695 white stoneware casting slip. I find that when my pieces bisque-Fire, the colors looks vibrant and promising. But once they are fired to cone 6, the lighter greens and blues become a washed out gray or brownish color. I am not using any glaze over the raw clay, so I’m not sure what is causing the color to change so much (reds and darker blues do just fine). Any ideas? I have read that the percentage of stain in the slip might be the cause, but I’m not sure why a higher percentage would change the actual COLOR from green to gray, versus just making it a more VIVID/deeper green (Which is the case with the reds I’ve used). Thanks for any help!

  3. I am having the same issue - although I’m not using glaze at all. So it must be that I used too high of a percentage of the stain. It’s interesting that with stains on other parts of the color spectrum, higher concentrations yield more vivid colors - but apparently not with light greens and blues! They just turn grey :P

  4. Hello,

    After reading many posts on the subject in this forum and others,  I remain deeply confused about the dangers of a bit of plaster being present in clay during firing. Many people take it as a given that even a speck of plaster embedded in clay will cause an “explosion” or, at the very least, cracking. They say this has to do with the different properties of the plaster, which will not shrink at the same rate as the clay that surrounds it.

    Many other folks say that the only danger with plaster in clay is that it can lead to “lime pops” AFTER firing.  They say that the plaster calcines during firing and then absorbs water later, which causes problems, but nothing that happens chemically during the firing itself will harm the piece. 

    Still others say it depends on the size of the piece of plaster in the clay.

    It seems to me like there must be some basic chemistry to all of this and the contradictory information is baffling to me. Does plaster pop out or melt into the clay body? does it shrink or expand? Is there a difference between what it does at bisque temperatures versus cone 5 or 10? Can anyone make sense of this? 

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