ok i am just a newbie, so this will sound stupid-- what exactly is the purpose of "bisque" firing, what is it, is it really needed or can a piece simply be maybe dried out for a month? I think it is a sort of low-temp prefiring to get all the water of the clay?
Bisque firing is done to get alot of the moisture out of the clay - there are certain chemicals that need to be burnt off before glazing. It also makes the piece hard enough to handle safely without it crumbling to pieces. It is possible to once fire a piece - that is let it dry, glaze it and fire it to glaze temp. This is a tricky process though because of those chemicals that burn out at lower temps (hence the bisque firing). Handling a bone dry piece is tricky too. That is when the piece is most fragile and can be cracked, broken and cruble. There are those on the list who can give youa more precise answer then this but this is my amount of knowledge.
=o) =o) =o) =o) =o) =o) Penni Stoddart Literacy Education Assistant Potter London, Ontario
Sometimes we just need to remember what the rules of life really are... You need only two tools: WD-40 and duct tape. If it doesn't move and it should, use WD-40. If it moves and shouldn't, use the duct tape.
Thank you Penni ! (CLayslinger)
Ok laugh your head off, i am sure this will sound stupid, but... could i bisque pieces in an ordinary kitchen oven, since it can heat up to 450 degrees Farhenheit, etc.? The kiln I will use to fire to Cone 6, etc. is across town, so it sure would be convenient to bisque in my home oven. Or is thus just a crazy idea and wacko?!? LOL.
No, you can't bisque fire in a home oven. Besides the fact that it's not hot enough, you must vent the kiln while firing bone dry greenware to bisque, or glazed bisque ware. The fumes created by firing pottery are noxious, and must absolutely not be done in a home oven.
Beowulf, please get a few books on pottery from your local library. You need an overall grounding before you proceed any further, in order to avoid wasting your time as well as harming your health. Unless, of course, you're just trolling. There are many basic pottery books which will answer your questions.
Cheers, Suzan
Historically raw or single firing was generally the norm. Biscuit firing was brought in mainly by the industrial potters because it allowed volume handling and glazing in a factory setting. It was subsequently adopted by non-industrial potters because it allows you more freedom and choice in glazing and decoration. After years of biscuit firing I have returned to single fire because for me it means I can complete the piece during the making, without interruption.
Steve Bath UK
In article , Suzan writes
On Sun, 14 Dec 2003 02:52:36 +0000, Suzan wrote: ..
Susan, several books on pottery, ceramics, and glazing are on the way from amazon, ordered them last week, they should arrive any day now. I just like asking questions, pondering the possibilities. Not trolling, honest. I have a wheel and have made several pieces, and called yesterday to the local ceramics supplier that does up to ^8 firing-- they said they will let me fire a whole batch (20+ pieces) for about $20 dollars-- things are looking good!
Beowulf,
Tried to send this message directly to you instead of the newsgroup. I guess you are intentionally being anonymous.
Folks aren't trying to be mean or discouraging when they suggest you read some books or take a class, they are honestly giving you the best advice they have. Some of your questions are so "newbie" they are a bit terrifying.
Most of us took classes or worked directly with a knowledgeable potter for years before we launched on our own. Personally this approach was invaluable to me. Throwing pottery is something that honestly takes years to learn and master.
Your enthusiasm is wonderful but I am afraid that it might be getting you in over your head. There is no chance that you will think to ask all the questions you need to know. We don't want you to kill yourself.
Specifics about the bisque cycle.
1- The bisque cycle is done in a kiln.2- The bisque cycle takes about 17 hours (with large variance) to complete.
3- The pieces should to be bone dry before placing in the kiln.4- The pieces can actually touch when they are being bisqued.
5- Some folks do not use shelves and stilts when putting pots in the bisque. This is a more advanced technique and I do not recommend it for at least the first 20 bisque firings you do. (unless you have an expert to help)6- The purpose of the bisque firing is to burn off impurities, and make the piece easier to handle in the glazing stage. (You need to know what type of glazes you will apply to make this choice. Glazes are formulated differently for pots including a bisque cycle and those are single-fired.)
7- At this point in time, using a bisque cycle is the standard in the US and single-firing is a generally only done by advanced potters or traditionalists.8- Each potter controls the bisque cycle differently.
9- Some clay bodies specify the bisque "cone" they recommend. If this is your case use the recommended cone.10- Otherwise, I recommend bisqueing to 06-04 range if you are doing a glaze fire to Cone 6 - 10. Personally I bisque to 04. I find I have fewer problems with the glaze if I do this higher "heat work". This is especially true for large pots. Your glaze fire temperature must match the maturation cone. Commercially available clay states a glaze firing cone range. Glaze firing higher than recommended will ruin your pots - they will melt. Glaze firing lower than recommended and they will not be vitrified and therefore will not hold water/food. (Note I am assuming you are not using low fire clay.)
11- The kiln (and the room the kiln is in) must be vented appropriately. Potters have died from inadequate ventilation. This is not an exaggeration or a long term cumulative effect.12- In the bisque cycle I recommend raising the temperature slowly until the kiln is at ~ 212F. I do this with my spy holes open at least for part of the time.
13- I also recommend raising the temperature slowing when you get to within 200F degrees of the endpoint.14- I usually soak at my top bisque firing temperature for 10 minutes
15- I generally let the kiln cool naturally after holding the bisque temp. On a glaze fire and sometimes with porcelain bisque I ramp the kiln down.16- I usually wait until the kiln has cooled to 200F before pulling the spy hole plugs and cracking the lid. Probably overly cautious.
17- The color of bisqued pieces range from gray to white to pink to light brown. Don't worry the clay color will change again during the glaze fire to match the promised color. This is especially true if you are using a gas kiln.Other notes/thoughts:
- Bisque pieces are not the final size of your pieces. They will shrink more in the glaze firing.
- Bisque pieces will need to be dusted off before applying glaze.
- If you are responsible for making your own glazes you need to be careful and accurate. Careful since some of the glaze materials are hazardous to your health. I use a respirator mask with replaceable cartridges that is approved for use with silica - a dusk mask does not adequately protect you. Accurate in that I recommend a triple-beam balance or equally sensitive electronic scale. A kitchen scale is not accurate enough to properly make glazes. If you will be firing to Cone
6 then I recommend "Mastering Cone 6 Glazes" by John Hesselberth & Ron Roy. I think this is an excellent book. Frankly, since you are doing this by yourself, I recommend buying premixed commercial glazes until you are more comfortable with the other aspects of creating pottery. They are more expensive and in the long term probably not what you will want. They will get you started and running. (The people in charge of the kiln won't be thrilled if you misformulate a glaze and it ruins their shelves and/or someone elses work. There should be no glaze on the bottom of the pot. Depending on how runny your glaze is then I also recommend a band of bare clay on the bottom of the sides. (I generally leave 1/4".)- When you talk about glazes you also need to know if the kiln is an oxidizing or a reducing environment. There are different glazes for the two environments. If it is an electric kiln you have access to then it will be an oxidation environment. (There are weird things you can do to make it reduction but ignore these more advanced techniques for now.)
Hopefully, someone else will bisque and glaze fire your pieces at least the first few times.
Good Luck,
Kobey
On Sun, 14 Dec 2003 18:15:30 -0600, Kobey wrote: ...
Yes, spam 'bots' peruse newsgroups for email addresses to add to spam address databases-- prudent to spoof one's email address in newsgroups
Wow thank you for the lengthy and valuable explanation. So much to learn!
First, there are no stupid questions.... The purpose of the bisque firing is to make the ware hard enough to accept glaze and wax resist or hot wax... If you bisque too high, the ware will not accept the water from the glaze and the glaze sit on top of the pot and chip off. I have done once fired stoneware. Its more difficult but saves gas as the ware is then fired only once eliminating the need for a bisque. The once fired work is easily damaged, because it green ware being dipped or brushed with glaze. Decoration is only one glaze on thinly. So this is ok for planters with say a temoku and albany slip clay underneath carved thru. (look up Straffito.) Many people bisque fire at 08 for gas fired stoneware and porcelain. Electric firing potters that glaze fire to cone 6 seem to like to bisque higher at cone 06. Personally, I stack my 120 ft downdraft very tightly with ware in the flue area and on the bagwalls... some of the ware is bisqued at 016 while most is going to be around 08. There are a few pieces right above the bag walls that are in the cone 1 range. Russell
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