Jenni Posted May 16, 2014 Report Share Posted May 16, 2014 I have been given everything in a home pottery studio from a deceased estate. Now that I have the kiln refurbished and running I am trying to work out what is in the buckets because the labels just have a word or two. From one bucket I've poured a very milky 'choc-mint' onto some terracotta cake plates. Because it was so pale I assumed it was a glaze and that the chocolate and greeny mint colour would come forth in firing. Also because I didn't know if it was food safe, I painted it over with a transparent glossy glaze. Surprise, surprise with the firing! Wherever I painted transparent glaze the choc-mint was now a brilliant aquamarine blue and elsewhere the 'choc-mint' was still milky. I'm not sure if the difference comes across well in these photos but in real light a difference is very evident. So are the contents of this bucket a slip? Would a slip's colour change that much under a coating of transparent glaze? Is there any way (apart from firing) to tell if what's in the other buckets are slips or glazes? Link to comment Share on other sites More sharing options...
Guest JBaymore Posted May 16, 2014 Report Share Posted May 16, 2014 Welcome to the forums. Ceramic raw materials and the fired results of using them typically have little to no relationship color-wise. Just something you learn to deal with. Yes... it could be slips. As to the food safeness questions.... a transparent glaze over anything is no guarantee of that concept. Complicated subject. See the sticky pinned at the top of this forum section called FAQ. Also maybe see this thread ... it sort of relates to getting "unknown raw materials": http://community.ceramicartsdaily.org/topic/4853-what-can-i-do-with-these-raw-materials/ best, ........................john Link to comment Share on other sites More sharing options...
neilestrick Posted May 16, 2014 Report Share Posted May 16, 2014 It could be a slip, but it could also be a higher firing glaze, which is why it's so dry and matte at terra cotta temp. If you've got some stoneware clay you could test it on, I would try firing it up to cone 5 and see if it melts out. Link to comment Share on other sites More sharing options...
JLowes Posted May 16, 2014 Report Share Posted May 16, 2014 May I suggest making a bunch of test tiles and doing some experimenting with the mystery buckets? Use different combinations, firing temps, under clear, etc. Then once you have it figured out, use the glazes/slips on the outside only, with a known liner glaze, for safety. John Link to comment Share on other sites More sharing options...
Mark369 Posted May 16, 2014 Report Share Posted May 16, 2014 I would put the test tiles in a clay tray to catch the run off if any. would hate to ruin shelves or kiln. Link to comment Share on other sites More sharing options...
timbo_heff Posted May 16, 2014 Report Share Posted May 16, 2014 Get rid of them... you don't know what it is, don't use it. Link to comment Share on other sites More sharing options...
williamt Posted May 16, 2014 Report Share Posted May 16, 2014 Test, don't use on functional, food ware. Could be interesting on sculptural pieces. There is a problem with disposal since you don't know what it is. I have a problem with just dropping stuff in the trash if I don't know what it is. Also, you say there is a word or two on each bucket. Is it anything that might give you a clue that it is a commercial glaze? Still a long shot, and your still not sure. But if you could match up some of those words it might give you a chance at narrowing down possibilities by comparing your tests to color charts. Lee Link to comment Share on other sites More sharing options...
clay lover Posted May 18, 2014 Report Share Posted May 18, 2014 What are the words on the buckets? Some of us might be able to ID something...... Link to comment Share on other sites More sharing options...
TJR Posted May 18, 2014 Report Share Posted May 18, 2014 I inherited some mystery buckets of glaze from my wife's cousin. He was a potter who died at age 53. Long ago now-10 years? Anyway, the buckets are falling apart and splitting. Had to either pitch them or test them. I knew they were stoneware glazes. Couldn't tell anything from the dried lumps in the bottoms of the buckets. There are five glazes. Two I slaked down, sieved and tested. One is a BEAUTIFUL temmoku glaze. One looks like a Mammo matte-kind of a white matte. I am reluctant to pour glazes down a drain as I try to walk softly on the back of mother Earth. I will use them and test the others. Unfortunately, I don't have the recipes. Lesson learned-mark your glaze buckets with the name and temperature [cone] of the glaze. You never know when your time is up! [imagine a picture of a scull right here, and spooky music.] TJR. Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted May 19, 2014 Report Share Posted May 19, 2014 I wonder who will end up with my bucket marked 'green of the unknown' Link to comment Share on other sites More sharing options...
Guest JBaymore Posted May 19, 2014 Report Share Posted May 19, 2014 I wonder who will end up with my bucket marked 'green of the unknown' The EPA. best, ....................john Link to comment Share on other sites More sharing options...
PSC Posted May 23, 2014 Report Share Posted May 23, 2014 I deal with mystery glaze all the time. As a nonprofit center we get donations of stuff...some good stuff, some not so good stuff and a lot of badly labeled stuff. As a nonprofit class with no budget i take it all and figure it out. I find often a google search of what is on the label might help find a brand or recipe that will help. If any books came with the donation often you can figure what the label means as it is a recipe from one of them. Figure what cone it fires to by testing it in kiln firings...place it in a catch plate so if it flows it won't ruin your kiln. If you can't get an i.d. from a google search use it only for non functional items. Btw for the benefit of who gets your stuff after you shuffle off this mortal coil don't use masking tape to label with, it dries out and falls off. Link to comment Share on other sites More sharing options...
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