sparklingmango Posted April 10, 2015 Report Share Posted April 10, 2015 Hello all. I put my Egyptian faience pastes into action yesterday and using my kiln for the first time. I was wondering if anyone could give some advice. The paste I fired was around two months old, and I left them dry for a total of 72+ hours while they create an efflorescence crust. My pieces were fired for around 6 hours, and I dropped the temperature from 900-700 degrees three times to allow the alkaline to fuse. However, the glaze on my piece did not come out as thick as expected. I think this is because the paste was not "fresh" and because I left it dry for too long. Most of the moisture left the piece which meant that this hindered the glaze. (please see image 1). I'm not sure if any of you are familiar with Egyptian faience. So I will attach some photos with this. The attached image of the necklace is Egyptian Faience - however which a much thicker glaze. Any opinonios/advice would be awesome, thank you :-)I am trying to prepare for my attempt 2. This is a project I am doing with my University, so there are time constraints on the amount of experimentation I can carry out. Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted April 10, 2015 Report Share Posted April 10, 2015 Where are you getting this firing cycle from? Seems odd to drop the temperature three times to 700. They look quite close to me but underfired. If when the pieces dried they did create an efflorescence crust then I think there may be nothing wrong with using old paste. How are you making the paste? Link to comment Share on other sites More sharing options...
sparklingmango Posted April 10, 2015 Author Report Share Posted April 10, 2015 Where are you getting this firing cycle from? Seems odd to drop the temperature three times to 700. They look quite close to me but underfired. If when the pieces dried they did create an efflorescence crust then I think there may be nothing wrong with using old paste. How are you making the paste? Because of my equipment I could not control the temperature. I could only read it and change the dial of my infinity switch. These pieces were fired at a total of 6 hours out of the 9 hours, I stopped this at 6 hours because they looked like they were about to crack. Also, they had not changed a lot from 4 hours in. I started to fire them at 900 and every hour, I dropped this temperature and then put the temperature back up again. CHEMICAL FORMULA PERCENTAGE VOLUME SILICA SiO2 87% 90g SODA ASH Na2O3 4% 4g WHITING CaO 4% 4g COPPER OXIDE CuO 0.5-1%* 1g BALL CLAY -- 4% 4g WATER H2O * 20ml Link to comment Share on other sites More sharing options...
maga Posted April 10, 2015 Report Share Posted April 10, 2015 If you stored the paste in dry state it shouldn't go to old. Your chemical composition has quite small amount of soda. I'm using similar composition but with soda ash about 8-12%. Figures on your picture looks to me underfired, Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted April 10, 2015 Report Share Posted April 10, 2015 So you are starting at 900 deg and then dropping the temperature to what every hour? Where did you get the idea to do this? If you were to plot the temperature on a graph what would the line look like? This is what most ceramic firing curves look like, a slow rise up to the top temperature with a hold and maybe controlled cool back to room temp. If you stored the paste in dry state it shouldn't go to old. Your chemical composition has quite small amount of soda. I'm using similar composition but with soda ash about 8-12%. Figures on your picture looks to me underfired, How do you fire your paste? Link to comment Share on other sites More sharing options...
maga Posted April 10, 2015 Report Share Posted April 10, 2015 So you are starting at 900 deg and then dropping the temperature to what every hour? Where did you get the idea to do this? If you were to plot the temperature on a graph what would the line look like? This is what most ceramic firing curves look like, a slow rise up to the top temperature with a hold and maybe controlled cool back to room temp. If you stored the paste in dry state it shouldn't go to old. Your chemical composition has quite small amount of soda. I'm using similar composition but with soda ash about 8-12%. Figures on your picture looks to me underfired, How do you fire your paste? 800 - 850 C with 30 min hold at 500 and 30 min hold on top temp. Link to comment Share on other sites More sharing options...
jolieo Posted April 10, 2015 Report Share Posted April 10, 2015 Below are some recipes I found online. Just from scanning and no true knowledge( I am a beginner) , you might not have enough soda in there for it to act as a flux or melter. You don't need to keep going up and down with temperature. You do need to get a temperature that melts the ingredients. Weird ( to me) thing about clay is a lot of the ingredients have a very high melting point on my here own, but if some of another ingredient is added, it melts at a much lower temperature. Egyptian paste recipes very somewhat. Generally, about 60% of the body will be non-plastic material; there will be at least 10% of a sodium-bearing material such as soda ash, bicarbonate of soda, or borax; and there may be up to 20% clay. Basic Egyptian Paste Ball clay 20 Soda feldspar 35 Silica 35 Sodium carbonate 10 *** Egyptian (turquoise) blue: 3% copper carbonate EUP Egyptian Paste Soda feldspar 38 Silica 38 Ball clay 12 Soda ash 6 Sodium bicarbonate 6 *** Egyptian blue: 3% copper carbonate *** Blue: 2% cobalt carbonate Egyptian Paste II Soda feldspar 38 Silica 19 Kaolin 13 Ball clay 5 Sodium bicarbonate 6 Soda ash 6 Calcium carbonate 5 Silica sand 8 *** Egyptian blue: 3% copper carbonate *** Blue: 2% cobalt carbonate Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted April 11, 2015 Report Share Posted April 11, 2015 I noticed something in the OP's formula that is going to mess with the advice everyone is offering: the OP is measuring by VOLUME, and we all assume weight measurements, because that's ceramic standard. 4% soda ash by volume will look like a different animal than by weight. But I agree that the pieces are likely under fired, and heating and cooling it the way you describe seems highly unnecessary. Re-fire the existing pieces by gradually turning up the heat once an hour or so, being very careful around the Quartz inversion point. Hold until the glaze looks smooth and shiny in the kiln and cool slowly. Ancient Egyptians didn't have Orton Pyrometric cones, they probably fired by eyeball, too. Link to comment Share on other sites More sharing options...
David Woodin Posted April 11, 2015 Report Share Posted April 11, 2015 You probably would do better by trying to hold the top temperature instead of cycling up and down. You can reglaze the pieces and fire again with a hold. I didn't think that clay was used in the ancient recipes. David Link to comment Share on other sites More sharing options...
maga Posted April 11, 2015 Report Share Posted April 11, 2015 I noticed something in the OP's formula that is going to mess with the advice everyone is offering: the OP is measuring by VOLUME, and we all assume weight measurements, because that's ceramic standard. 4% soda ash by volume will look like a different animal than by weight. Good point, but, soda ash is 4% and 4g in 103 total. Question is, what is the correct value. Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted April 11, 2015 Report Share Posted April 11, 2015 To me it looks like they are using the term volume for weight. Weird xD CHEMICAL FORMULA PERCENTAGE VOLUME SILICA SiO2 87% 90g Anyway, whatever the recipe it is close to other paste recipes, right? Concentrate on sorting out the firing first. Link to comment Share on other sites More sharing options...
maga Posted April 11, 2015 Report Share Posted April 11, 2015 Where are you getting this firing cycle from? Seems odd to drop the temperature three times to 700. They look quite close to me but underfired. If when the pieces dried they did create an efflorescence crust then I think there may be nothing wrong with using old paste. How are you making the paste? Because of my equipment I could not control the temperature. I could only read it and change the dial of my infinity switch. These pieces were fired at a total of 6 hours out of the 9 hours, I stopped this at 6 hours because they looked like they were about to crack. Also, they had not changed a lot from 4 hours in. I started to fire them at 900 and every hour, I dropped this temperature and then put the temperature back up again. AFAIR she is using small kiln for metal clay without controller, so it'll be hard to make reasonable firing. @sparklingmango How big are those item on photo ? Link to comment Share on other sites More sharing options...
sparklingmango Posted April 11, 2015 Author Report Share Posted April 11, 2015 Ok, I shall try and reply to all! Sorry I'm an Egyptologist, so I am not very good with this chemistry/ceramics shizz, so you'll have to bare with me Volume = weightIt was my first time firing, so this was an experiment if anything. Here I will attach a link of a table I created of the firing pattern. Please see for more info. It was stopped with 3 hours left. (hense why it doesnt go to the end...)Yes, in the Egyptian recipes they did use some sort of clay. I got this recipe from a PhD Dr who is an expert in Egyptian Faience so I know that pretty much it is correct. Plus, the first firing following this came out pretty well for my first time so I think I am on the right track here atleast. ?? If you want to see more about recipes please see Paul Nicholson or Pamela Vandiever. Fortunately, I have my own kiln so this week is going to be a lot of experimenting to find a good firing cycle for faience. Tomorrow I plan to do some experimentation with the firing cycles. Like David said I am going to try and hold the higher temperature rather than drop it. Although, because the pieces were underfired (it is hard to see in the pic) but it looks like they were pretty much on there way to getting a good glaze. TIME REMAINING TEMP DIAL NO. NOTES 8 hrs, 35 mins 935 °C 8.5 8 hrs, 16 mins 816 °C 5.3 8 hrs, 4 mins 789 °C 5 8 hrs, 1 mins 1 First drop down hour to 100 °C 7 hrs, 46 mins 585°C 1 7 hrs, 33 mins 474°C 1 7 hrs, 25 mins 405°C 1 7 hrs, 5 mins 312°C 1 6 hrs, 51 mins 260°C 1 6 hrs, 37 mins 626°C 8 Turned dial back up to 8 6 hrs, 7 mins 880°C 8 5 hrs, 52 mins 917°C 8 Dropped down to 7 dial to maintain suitable temperature 5 hrs, 36 mins 905°C 7 Dropped down to 6.8 dial because temperature was too high 5 hrs, 27 mins 873°C 6.8 5 hrs, 16 mins 865°C 6.8 Dropped down to dial 6 to maintain faience temperature 5 hrs, 7 mins 838°C 6 Dropped down to dial 2 to start the second cycle of cooling down 4 hrs, 56 mins 732°C 2 4 hrs, 43 mins 599°C 2 4 hrs, 30 mins 511°C 2 4 hrs, 19 mins 459°C 2 4 hrs, 9 mins 417°C 2 Dropped to dail 1 for a lower temperature 3 hrs, 49mins 309°C 1 Changed dial to 7 to get a higher temperature 3 hrs, 38 mins 508°C 7 3 hrs, 20 mins 693°C 7 Changed dial to 8 to get a higher temperature Thanks for all your advice dudes. Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted April 11, 2015 Report Share Posted April 11, 2015 That sure is the craziest firing I have seen. You went room temperature to 900degC in 25 min! There is no way you need to be dropping the temperature, or getting to 900degC in 25 min. Who told you to fire this way? What do you mean when you say 'maintain faience temperature' What is faience temperature? I would think a firing cycle would be something like this. Seeing as the clay can take being heated up fast in 25 min I think you can easily shorten your 9 hour firing cycle. 0-1 hours on setting 1. 0-2 hours on setting 4. 0-1 hours on top setting till you reach top temp. Hold temp for half an hour Link to comment Share on other sites More sharing options...
sparklingmango Posted April 11, 2015 Author Report Share Posted April 11, 2015 That sure is the craziest firing I have seen. You went room temperature to 900degC in 25 min! There is no way you need to be dropping the temperature, or getting to 900degC in 25 min. Who told you to fire this way? What do you mean when you say 'maintain faience temperature' What is faience temperature? I would think a firing cycle would be something like this. Seeing as the clay can take being heated up fast in 25 min I think you can easily shorten your 9 hour firing cycle. 0-1 hours on setting 1. 0-2 hours on setting 4. 0-1 hours on top setting till you reach top temp. Hold temp for half an hour hahaha i know right, it is crazy!! I was told to do 900 degrees and then drop to cool down at 100 degrees, but i dont really know what that meant. so, i just went a bit crazy with the first attempt to see what it would turn out like. my main objective was to get up to around 900 degrees and then just slowly drop it down and bring it up again, i have recorded it so much because i do not have a controller and for future reference (too improve the firing cycle!) ok, awesome, i shall try this way. i was hoping to create something like that, i just need to experiment more. I shall let you know how the next one goes, hopefully with less crazy and more glaze! Link to comment Share on other sites More sharing options...
sparklingmango Posted April 15, 2015 Author Report Share Posted April 15, 2015 That sure is the craziest firing I have seen. You went room temperature to 900degC in 25 min! There is no way you need to be dropping the temperature, or getting to 900degC in 25 min. Who told you to fire this way? What do you mean when you say 'maintain faience temperature' What is faience temperature? I would think a firing cycle would be something like this. Seeing as the clay can take being heated up fast in 25 min I think you can easily shorten your 9 hour firing cycle. 0-1 hours on setting 1. 0-2 hours on setting 4. 0-1 hours on top setting till you reach top temp. Hold temp for half an hour I kind of used your firing cycle. I modified it a bit though, 0-1 hours to 1 then 2, 0-2 hours to 6 and then 7. high temp then cool down. Total firing 5 hours and a half here are the results, much better than the first Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted April 15, 2015 Report Share Posted April 15, 2015 Great They look much more glassy. The bigger figure looks a little dull so it could be worth trying next time to go even slower through the last 100 deg of temperature rise to get the heat into the bigger pieces. Most of the melting will take place here and if you go too quick things don't get enough time and temperature to melt. Link to comment Share on other sites More sharing options...
Briantllb Posted May 8, 2019 Report Share Posted May 8, 2019 do you guys seriously thing the ancient Egyptians had kiln controllers? Link to comment Share on other sites More sharing options...
Hulk Posted May 8, 2019 Report Share Posted May 8, 2019 Some rely on colour (red -> orange -> yellow -> white ...ooh, that's hot!) only, even today in the "...fascinating modern age we live in." - and do quite well with it (be sure to wear appropriate eye protection!! !!! !!!!). Me, well, I'm watching the thermocouple readout an' pyrometric cones. Link to comment Share on other sites More sharing options...
liambesaw Posted May 8, 2019 Report Share Posted May 8, 2019 2 hours ago, Briantllb said: do you guys seriously thing the ancient Egyptians had kiln controllers? No, they had hundreds of generations of trial and error passed on from father to son. That's way better than a kiln controller. Unfortunately most of the potters I know only have the one lifetime to achieve what they need Plus when firing with wood, you are the kiln controller ;). We can.try to mimic the variation and hurdles involved with fuel firing by manipulating our controllers. Link to comment Share on other sites More sharing options...
oldlady Posted May 8, 2019 Report Share Posted May 8, 2019 mango, now that you are on the right track, may i suggest something else? your necklace has a good line (design) from right to left and back again EXCEPT for the one piece that dangles to a point. that one should be in the center to balance the whole arrangement. Link to comment Share on other sites More sharing options...
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