Luca Ask Posted February 20, 2021 Report Share Posted February 20, 2021 Last year I decided to resume my passion for modeling clay and in particular stoneware and porcelain clay. I decided to specialize in single firing (I had a book taken in Scotland several years earlier). At the moment I'm cooking at 1240°C, non-stop. The cooking lasts 3 hours between 0 and 200°C and then travels at a speed of about 100°C per hour (if I remember correctly: the oven is not mine). I'm doing glazes experiment using wood ash. This idea came from the fact that we use the fireplace and in particular the pellet stove for the winter. Wood ash from the pellet stove is probably not ideal: because some of the finer particles are lost and the sieve work is longer and give a coarser material. But I have a lot of ash from this stove and it's a shame not to use it, if possible. I had some book from Scotland about ash glazes and cone 6 glazes and I'm starting from them. To make my life easier, I use wood ash washed several times but I do not dry it: I let it settle and remove the surface water leaving only about 1 cm of water. At the beginning I used a volumetric system in the first 2 recipes (photos). Recipe 1: - 1 jar of dense slip of 1250°C spotted stoneware clay - 1 jar of thick potassium feldspar slip - 2 jars of dense wood ash slip Recipe 2: - 1 jar of dense slip of porcelain clay - 1 jar of thick potassium feldspar slip - 2 jars of dense wood ash slip. Than I made 2 little experiment with a little of cobalt and copper oxide. I calculated that those slips contain about 50% water and 50% clay or feldspar. Instead, I estimate a quantity of about 300 grams of dry ash in a liter of ash slip. The calculation is very approximate but the second experiment I am conducting is based on this hypothesis. Now I bought the different dry raw materials and a precise scale, so I weighed the ingredients precisely. However, I still use a very dense ash slip instead of dried ash: drying the ash would be too much work at the moment. I'm preparing the basic recipes for the next experiments. For now I have prepared the first two recipes based on the first experiments: First recipe: - 1 kg potassium feldspar - 1 kg ball clay - 170 gr bentonite - 500 ml pheatine - 2 liters of water - 4 kg dense ash slip Second recipe: - 1 kg potassium feldspar - 1 kg china clay - 170 gr bentonite - 500 ml pheatine - 2 liters of water - 4 kg dense ash slip I'm looking for other simple basic recipes to try. Something that can introduce someting new for the experiments with oxides. I have tried to modify some recipes of "Glazes cone 6 1240°C" book of Michael Bailey: exchanging whiting with wood ash, dolomite with wood ash and talc, exchanging soda feldspar and litium carbonate with spodumene, adding 5% bentonite for single firing. I am trying to modify a cone 8 recipe of the book "colour in glazes" of Linda Bloomfield exchanging soda feldspar with spodumene and calcium borate frit with colemanite, exchanging whiting with wood ash and using a litle less quartz hoping to fire successfully at 1240°C instead of cone 8. Looking to my books these are some ideas to try: Recipe 3 (recipe T13 modified from Michael Bailey book): 830gr soda feldspar, 130 china clay, 140 bentonite, 430 quartz, 120 Zinc oxide, 1,5 kg wood ash dense slip. And pheatine. Recipe 4 (recipe T14 modified from Michael Bailey book): 1kg spodumene, 500gr china clay, 160 gr bentonite, 500gr dense wood ash slip, 100gr talc, 100gr zinc oxide, 240gr quartz. Recipe 5 (recipe OR1 modified from Michael Bailey book): 1kg spodumene, 130gr china clay, 150gr bentonite, 322gr bone ash, 16gr litio carbonate, 362gr talc, 244gr quartz Recipe 6 (recipe for chromium green modified from Linda Bloomfield book): 1000gr spodumene, 320gr colemanite, 1000gr dense wood ash slip, 107gr china clay, 300gr quartz, 107gr bentonite. I hope to use this recipe with chromium to obtain a green glaze. Link to comment Share on other sites More sharing options...
Luca Ask Posted February 20, 2021 Author Report Share Posted February 20, 2021 Link to comment Share on other sites More sharing options...
Luca Ask Posted February 20, 2021 Author Report Share Posted February 20, 2021 In the first photo there are the tests. From left to right, up down: Recipe 1 , left 2 layers, right 1 layer Recipe 2, left 2 layers, right 1 layer Recipe 1 with cobalt oxide Recipe 1 wih 50% cobalt and 50% red copper oxide Recipe 1 with red copper oxide Only houses are with the wood ash glaze (recipe 1 one layer) Link to comment Share on other sites More sharing options...
Min Posted February 21, 2021 Report Share Posted February 21, 2021 2 hours ago, Luca Ask said: I'm looking for other simple basic recipes to try. This one is super runny. If it's too runny for your purposes then increase the clay content. I'm not familar with pheatine, is this a brushing medium or gum? Link to comment Share on other sites More sharing options...
liambesaw Posted February 21, 2021 Report Share Posted February 21, 2021 Pehatine for those of us in the US is brushing medium Link to comment Share on other sites More sharing options...
Luca Ask Posted February 21, 2021 Author Report Share Posted February 21, 2021 7 hours ago, Min said: This one is super runny. If it's too runny for your purposes then increase the clay content. I'm not familar with pheatine, is this a brushing medium or gum? Thanks very much. Pheatine is a brush medium. I'm trying to use it (and bentonite) also as suspending agent. At the moment I prefer to use glazes that are not very runny: I'm afraid for the kiln that is not mine! I'm also not sure that I'm firing to cone 6: I'm firing 1240°C but a bit slowly because of single firing. I can try to use it with washed ash and with more ball clay. Or china clay and bentonite in exchanging with ball clay i think. I have to try to create some pot in order to try to use it inside. Do you know if it is useful also with chromium for green? Link to comment Share on other sites More sharing options...
Min Posted February 21, 2021 Report Share Posted February 21, 2021 8 hours ago, Luca Ask said: Do you know if it is useful also with chromium for green? Your recipes numbered 3 and 4 won't give you a good green with chrome as there is zinc in the recipes. The one I posted should be okay but test it first. It's difficult to give opinions on your posted recipes for a couple reasons, first off we don't know the dry weight of the ash and secondly there is a bit of math gymnastics involved as the recipes don't total 100 so changing from grams and kilos and litres to try and sort out the percentages of each is a bit tricky. A cone 10 ash glaze can be as simple as 50 ash + 50 clay. We know that this in all likelihood won't melt well at cone 6 so some additional flux is necessary. Instead of trying a bunch of random recipes if I was approaching this recipe I would do a few triaxial blends. I don't know if you are familiar with these or not so please excuse this if you already know how to do them. If not, you use 3 ingredients blended in varying proportions to make a series of glazes. In this case you would use clay, ash and your choice of flux. For cone 6 flux I would try nepheline syenite in one triaxial and a blend of a high boron frit + feldspar (mixed 1:1) in another. Do a search for how to do a triaxial if this is something you want to try. You can make the triaxial as large as you want, diagram below of a 21 test tile one. This means that from 3 points you will get 21 glazes. (granted that in this case the tips of the triaxial are not going to be useable glazes) Once you get the base glaze sorted out then move on to colour testing with your chrome etc. Link to comment Share on other sites More sharing options...
Luca Ask Posted February 21, 2021 Author Report Share Posted February 21, 2021 1 hour ago, Min said: Your recipes numbered 3 and 4 won't give you a good green with chrome as there is zinc in the recipes. The one I posted should be okay but test it first. It's difficult to give opinions on your posted recipes for a couple reasons, first off we don't know the dry weight of the ash and secondly there is a bit of math gymnastics involved as the recipes don't total 100 so changing from grams and kilos and litres to try and sort out the percentages of each is a bit tricky. A cone 10 ash glaze can be as simple as 50 ash + 50 clay. We know that this in all likelihood won't melt well at cone 6 so some additional flux is necessary. Instead of trying a bunch of random recipes if I was approaching this recipe I would do a few triaxial blends. I don't know if you are familiar with these or not so please excuse this if you already know how to do them. If not, you use 3 ingredients blended in varying proportions to make a series of glazes. In this case you would use clay, ash and your choice of flux. For cone 6 flux I would try nepheline syenite in one triaxial and a blend of a high boron frit + feldspar (mixed 1:1) in another. Do a search for how to do a triaxial if this is something you want to try. You can make the triaxial as large as you want, diagram below of a 21 test tile one. This means that from 3 points you will get 21 glazes. (granted that in this case the tips of the triaxial are not going to be useable glazes) Once you get the base glaze sorted out then move on to colour testing with your chrome etc. Ok, thank you. I have a book that explain very well triaxial. I will try to do it. The fact is that I was very lucky with my first 2 recipes. For this reason my idea was to try some new recipes doing only a little triaxial before and, if necessary, after the first fire. I had read that with zinc oxide is not possible to obtein green from chrome and that affect also other colors and oxides: this has the reason for my last recipe. I hope it can be possible to have some green with the recipes that have not the zinc oxide. I have not bought nefeline syenite and boron frit at the moment. Why do you think can be better to try them instead of spodumene and colemanite? My idea was to use them to introduce litium oxide and boron. I will try to modify recipes in order to total 100 and to specify the dry wood ash hypothesis Link to comment Share on other sites More sharing options...
Min Posted February 21, 2021 Report Share Posted February 21, 2021 If you don't have a boron frit then yes I'ld try the colemanite to supply the boron. Spodumene could work too, have to try it and see. Link to comment Share on other sites More sharing options...
akilspots Posted February 22, 2021 Report Share Posted February 22, 2021 I've been doing some wood ash + clay + feldspar + frit biaxials lately. they have neen helpful when trying to discover new glazes. Link to comment Share on other sites More sharing options...
Sorcery Posted February 22, 2021 Report Share Posted February 22, 2021 Every time, these boys just nailed it! Found a lot of good information at Derek's site/'s too. https://derekau.net/2015/03/19/ash-glazes/ Sorce Link to comment Share on other sites More sharing options...
Luca Ask Posted February 22, 2021 Author Report Share Posted February 22, 2021 On 2/21/2021 at 5:56 PM, Min said: It's difficult to give opinions on your posted recipes for a couple reasons, first off we don't know the dry weight of the ash and secondly there is a bit of math gymnastics involved as the recipes don't total 100 so changing from grams and kilos and litres to try and sort out the percentages of each is a bit tricky. These are the modified recipes in order to total 100. Dry washed wood ash is calculated with my hypotesis. In the Recipe 5 I decided to use Cornish Stone and not spodumene (the original Michael Bailey Recipe use Potash Feldspar) Recipes 1 29,4 Feldspato pot. 29,4. Ball clay 36,2 Washed wood ash 5 Bentonite Recipes 2 29,4 Feldspato pot. 29,4. China clay 36,2 Washed wood ash 5 Bentonite Recipes 3 39,3 Feldspato sod. 6,2 China clay 21,8 Washed wood ash 6,6 Bentonite 20,4. Quartz 5,7. Zinc ox. Recipes 4 44,4 Spodumene 22,2 Ball clay 6,8 Washed wood ash 7,1 Bentonite 4,45 Talc 10,6 Quartz 4,45 Zinc ox. Recipes 5 (to have red with red iron ox.) 44,5 Cornish stone 3,8 China clay 14,3 Bone ash 6,6 Bentonite 16,1 Talc 10,7 Quartz 4 Litio carb. Recipes 6 (hoping to have green with chromium ox.) 46,7 Spodumene 5 China clay 14,4 Washed wood ash 14,9 Colemanite 5 Bentonite 14 Quartz Link to comment Share on other sites More sharing options...
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