larathompson288 Posted June 29, 2022 Report Share Posted June 29, 2022 Hi there, I am making plates for my sisters wedding present. I am using Velvet Amaco Lead Free Underglazes and it says 'fire to mature cone 05-04. I have put it on fired stoneware clay and would like the colour to be as bright as possible. I am using a Nabethern Kiln and was wondering what cone 05-04 meant in terms of degrees celcius per time period ie. it would be great to know the firing ramp schedule as I am not confident in cones. If anyone could help I would really appreciate it, Thank you! Quote Link to comment Share on other sites More sharing options...
Bill Kielb Posted June 29, 2022 Report Share Posted June 29, 2022 (edited) Are you familiar with heatwork and firing to cone? Here is a link to an Orton cone chart https://glazy.org/posts/156627. The important part to establish the expected heatwork is to follow the ramp speed posted in the column for the last 100c of the firing. Most folks follow the middle column and fire at 60c per hour for the last 100c. Cone 05 would be 1031c (from Orton table) - 100c = 931c. So last ramp starts at 931c is fired at 60c per hour and ends at 1031c for cone 05 Edited June 29, 2022 by Bill Kielb Rae Reich 1 Quote Link to comment Share on other sites More sharing options...
Min Posted June 29, 2022 Report Share Posted June 29, 2022 @larathompson288, many of the Velvets can go to cone 10 without loosing their vibrancy. Useful set of images here that shows the Velvets, each fired to cone 05 on the left, cone 5 in the middle and cone 10 on the right. (Orton cone chart that Bill linked will give you the temperatures for each of those) Super important to test the underglazes with the glaze you will be using them with as there can be colour shifts depending on the chemistry of the covering glaze. Many people use a zinc free clear as a covering glaze. You mentioned using a stoneware for the plates, what is the recommended firing temperature or cone for it? For dinnerware you want the clay to be as mature as possible for both strength and vitrification. Are you firing stoneware to earthenware temperature? (like cone 05) Rae Reich and Chilly 2 Quote Link to comment Share on other sites More sharing options...
larathompson288 Posted June 30, 2022 Author Report Share Posted June 30, 2022 9 hours ago, Bill Kielb said: Are you familiar with heatwork and firing to cone? Here is a link to an Orton cone chart https://glazy.org/posts/156627. The important part to establish the expected heatwork is to follow the ramp speed posted in the column for the last 100c of the firing. Most folks follow the middle column and fire at 60c per hour for the last 100c. Cone 05 would be 1031c (from Orton table) - 100c = 931c. So last ramp starts at 931c is fired at 60c per hour and ends at 1031c for cone 05 Thank you - this is really helpful. What temperate increase per hour do I use before the last hour when i do 60c between 931 and 1031? So, in terms of cones more generally, do they just refer to what to do in the last hour of firing? Thank you! Quote Link to comment Share on other sites More sharing options...
Bill Kielb Posted June 30, 2022 Report Share Posted June 30, 2022 (edited) It’s not the last hour, you fire at the rate of 60c PER HOUR for the last 100c so that will take a little more than 1 hour and a half (1:40 actually). With respect to cones, they are made of glaze and calibrated to show accumulated heat work which happens mostly in the last 100c This is where glaze mostly matures. Silica and alumina without flux don’t like to really melt below about 1600c flux helps things melt. The question becomes when? Because cones are glaze and glaze melts as a result of fluxes lowering the melting point and time and temperature affects accumulated work, cones more accurately show when a glaze is mature. Because they are made of glaze and calibrated to bend at their cone value. Think of it a little like cooking, if you leave your pizza in the oven and ignore time and cook it for 30 minutes more than the instruction, it’s probably well over done. Time and rate combine as something called heatwork. Cones are made of glaze and indicate accumulated heatwork on a glaze. Here is an interesting thought, if I reach 1031c and hold or soak for thirty minutes I now drive this from cone 05 to likely two cones higher in accumulated work or cone 03. Time And temperature affect glaze maturity. So to answer your last question, cones indicate what happens in about the last 1h40m of the firing, which is the most important part of the firing with respect to maturity. Edited June 30, 2022 by Bill Kielb Chilly and PeterH 2 Quote Link to comment Share on other sites More sharing options...
Bill Kielb Posted July 2, 2022 Report Share Posted July 2, 2022 (edited) On 6/30/2022 at 2:02 AM, larathompson288 said: Thank you - this is really helpful. What temperate increase per hour do I use before the last hour when i do 60c between 931 and 1031? Hmm misread this or it changed. The prior speed can be anything you like and your wares can tolerate. 100c - 250c range is common. Glaze firings generally can go fast. The heat work put in before the last 200c (to be conservative) in a glaze firing is fairly reversible. Bisque firings on the other hand generally take longer and depend on time and temperature to burn out all organics Edited July 2, 2022 by Bill Kielb Quote Link to comment Share on other sites More sharing options...
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