briano Posted March 29, 2020 Report Share Posted March 29, 2020 Beginners saggar question here... I tried a few small test pieces wrapped in tinfoil in a saggar made from grogged stoneware clay, and was very happy with results first time. Repeated this and was happy again with similar results, but unfortunately the saggar had cracked ...not sure how many times it may have been used before me. Without knowing how many firings I could expect to get from any saggars I might make myself, I decided to try it using terra cotta flower pot from garden center instead ...making just the lid myself instead of entire new saggar. Have tried same temperature around 1800degrees Fahrenheit and some lower temperatures but getting only very feint results. So... same kiln, same temperature, same test pieces, same combustible materials, same tinfoil and same size saggar ...BUT... handmade grogged stoneware saggar Vs terra cotta flower pot saggar Any helpful theories or suggestions on why these are performing so differently would be much appreciated! ...before I go ordering grogged clay to try make my own saggar Link to comment Share on other sites More sharing options...
Rae Reich Posted March 30, 2020 Report Share Posted March 30, 2020 You haven't described the difference in your results. What was different in the flowerpot firing? Link to comment Share on other sites More sharing options...
briano Posted March 31, 2020 Author Report Share Posted March 31, 2020 Hi, well the very feint results were almost nothing... just a bland pale grey I guess. No real pattern, just kind of dull ...as opposed to the distinct dark/light greys and contrasts I was getting with the grogged stoneware saggar. I'm wondering now whether maybe the terracotta flowerpot somehow stores up more heat during firing than the handmade stoneware saggar ...meaning that possibly the combustibles are working their magic at some point but that the effects then burn off maybe? - all guesswork on my part though, I'm not very knowledgeable on this. Link to comment Share on other sites More sharing options...
neilestrick Posted March 31, 2020 Report Share Posted March 31, 2020 Was the stoneware saggar fired to vitrification? If so, it could have something to do with the terra cotta being porous. It could also be due to cooling times, how they transfer heat, how the lid seals, etc. Lots of possibilities. Link to comment Share on other sites More sharing options...
briano Posted March 31, 2020 Author Report Share Posted March 31, 2020 Hmmmm..... unfortunately I can't tell now whether the first saggar was vitrified. It was made and left behind by somebody else, so I don't know what temperature they fired it to. Thank you for all those helpful pointers though. Link to comment Share on other sites More sharing options...
Rae Reich Posted April 1, 2020 Report Share Posted April 1, 2020 Flowerpot didn't have a hole in it, did it? Perhaps now that the flowerpot has been fired to your desired temperature, it will be tempered to that in subsequent firings? Link to comment Share on other sites More sharing options...
Magnolia Mud Research Posted April 1, 2020 Report Share Posted April 1, 2020 If the flower pot is significantly more porous, and if the porosity of the sagger is the cause of the defects in the fired ware, applying a coating of something that will "plug" the pores of might improve the technique. You can rub the flower pot with some dry kaolin or ball clay to fill in the pores on both the inside and outside. Or make a thin (terra sig thin or skim milk thin) slip with either kaolin or ball clay and a "pinch of baking soda) and apply to the flower pot to close up the surface pores. ( and Yes, Virginia, you can make a thin clay slip adhere by rubbing the slip into the pores of damp and/or dry bisque ware and porous flower pots). LT Link to comment Share on other sites More sharing options...
briano Posted April 2, 2020 Author Report Share Posted April 2, 2020 13 hours ago, Rae Reich said: Flowerpot didn't have a hole in it, did it? Perhaps now that the flowerpot has been fired to your desired temperature, it will be tempered to that in subsequent firings? Hole in base of flower pot was plugged with same clay I used to seal around the lid. And flower pot saggar has been used three times now (as I was testing and tweaking combustibles, tinfoil, etc) with no improvement in results unfortunately. - Still great suggestions for helping me tease this out though, thank you! 12 hours ago, Magnolia Mud Research said: If the flower pot is significantly more porous, and if the porosity of the sagger is the cause of the defects in the fired ware, applying a coating of something that will "plug" the pores of might improve the technique. You can rub the flower pot with some dry kaolin or ball clay to fill in the pores on both the inside and outside. Or make a thin (terra sig thin or skim milk thin) slip with either kaolin or ball clay and a "pinch of baking soda) and apply to the flower pot to close up the surface pores. ( and Yes, Virginia, you can make a thin clay slip adhere by rubbing the slip into the pores of damp and/or dry bisque ware and porous flower pots). LT Interesting suggestion, thanks. I don't think the flower pot is particularly porous, but that might still be worth a try. Can't access studio at the moment unfortunately, but will let you know if I do get round to giving that a go. Thanks to all for your helpful tips! B Link to comment Share on other sites More sharing options...
Rae Reich Posted April 2, 2020 Report Share Posted April 2, 2020 @briano, a red clay earthenware flowerpot fired to maturity will always be significantly more porous than stoneware fired to maturity. Additionally, earthenware is, generally, more dense than grogged stoneware. Link to comment Share on other sites More sharing options...
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