Chemistry basics for potters?

The first thing I would have recommended you do is to go to these sites and read what they have. There is more than you will ever want to know on the digitalfire site about chemistry. It is an excellent educational source. Frogpondpottery has a wonderful article on glaze stability. Both Masteringglazes and digitalfire have software for analyzing your glazes. I have a very primitive program for doing so but have given up on giving it out because I kept finding bugs in it that people never told me were there so I decided it was not safe for me to be sharing. Plus both digitalfire and masteringglazes software have experts behind the software that can give you the right answers to you questions.

examples chemistry is really not going to be of any use to you. In fact, the most you will really need to know, you probably already know. Potters work in the world of oxides - an oxide is a chemical compound containing one or more oxygen molecules. Next I would recommend you go to the clayart list - you have to join to post but you don't have to join to search. Many questions you would ask have already been asked.

?S1=clayart book I would recommend is Mastering Cone 6 Glazes by John Hesselberth and Ron Roy (see above site). While I really like this room it is for the most part relatively quiet (one of the reasons I like it). I think you would do better posting your questions in the other room. They have first class support there who check in regularly.

Donna

P.S. I checked the site where you get your glaze and clay and still have not been able to figure out what is what. They are not going to share the recipe of their glazes however so there is no way to help with the chemistry of your glazes. It would be good to know if you are underfiring your glaze but I can't find it from what you gave us. As I said however, any commercial glaze should not be giving you this problem if you are firing to the correct temperature.

Hi Maryanne

I have a book called "Ceramic Science for the Potter" by W.G Lawrence which gives LOTS of information about all technical aspects of ceramics, including glaze chemistry. If you wanted to do some serious study it's worth a look. It's an old book (1972) but today I found several copies on abebooks for as low as US$16. If you are interested I can post more information about the book.

Cheers

David

Chemistry is easy - it's just electrons. :-) Of course various areas of chemistry can get a bit complicated, but glaze chemistry is a very specialized area so you don't need a broad knowledge of the other stuff in order to learn how glazes work. Don't be put off by the odd names and symbols, it's a really just like cooking from a recipe - once you are familiar with the basic ingredients and have a feel for how they work together you will not only understand what the various ingredients contribute to the final result[1] but also be able to vary the recipes to get the result that you want (with a little experimentation).

[1] There's a bit of physics in there too, which basically determines how the glaze works with the clay you're glazing, but again it's more a matter of getting a feel for it rather than worrying about complex equations.

This site seems to offer a pretty good introduction to the basics

might help to allay some of your fears about 'chemistry'. :-)

This is a good book, but as David noted it takes "some serious study". I have a chemistry background and found it pretty heavy going. I certainly wouldn't start with it. FYI, it's been reprinted and is available from Axner's -

-though personally, I'd suggest getting an old copy if possible. Oldhardback books just have more character than new paperbacks. deg

Basic chemistry (or acidic chemistry... hee, hee!) probably won't be of much help with clay and glazes, which are pretty specialized. Some books that I have found helpful for the "big picture" are "Pioneer Pottery" by Michael Cardew, and "The Potter's Dictionary of Materials and Techniques" by Frank and Janet Hamer. If you don't have these, I'd recommend getting them just for general reference, especially the second one. (I put off getting that for a long time because of the "Dictionary" in the title... big mistake! It's not a dictionary at all, more like an encyclopedia... and it covers *everything* in great detail! I got an older edition from a used bookseller; still pricey, but well worth it.)

I also second the suggestion of "Mastering Cone 6 Glazes", and would also include "Glazes Cone 6" by Bailey.

There has been a series called "Back To Basics" by Pete Pinnell running in Clay Times. The latest installment (Part 4) is called "Making Sense of Unity Formulas". Covers the bascis well, and gives good advice.

The big problem is that it's a long way from normal chemistry to understanding what will make a glaze stiff or runny, glossy or matte, etc. Most of this comes down to us as "rules of thumb" which, although they do have a scientific basis, may be better than trying to figure things out from scratch. There are just too many variables, especially when you include the firing schedule, to do any serious prediction "de novo". But once you have a starting point, it is much easier to say "keeping everything else the same, more alumina will make this glaze less runny", or whatever.

Best regards,

Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis

Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!

Suggestions I got from another source

The Complete Guide to High-fire Glazes - by John Britt

Clay and Glazes for the Potter - by. D. Rhodes

The Ceramic Spectrum - by R. Hopper

... I'll get back to you guys - just need to make proper notes first.

Marianne

Just to show you how little I know of chemistry, I had to re-read that joke about 3 times before I got it!

_snip good suggestion_

Is there a table anywhere on the internet that shows the Celcius scale next to the cone scale? I read cone this and cone that and still don't have a clue what temp they are - and the cone 6 and cone 06 stuff is really confuzzling!

I am assuming that Clay Times is an American publication? It would cost me a fortune to get hold of issues of that. I do subscribe to the British magazine Ceramic Review, though, and that has had some seemingly good articles, but, as I said above, my knowledge is wayyyy to lacking as yet.

I do get what you mean, but then I would be winging it and not able to understand a little of WHY those substances do what they do. And that would mean that I would have less intuition about what else I could try to achieve what I want.

Thanks so much for your input. Your message has been saved on my computer, and I will take all the book suggestions and print them out for my next binge on Amazon :-)

Marianne

The thing is, I can't even tell you exactly what an electron is! That's how lacking my education is in this area. Had I known earlier, I might have taken a course somewhere, but I can't take a chemistry course here in Switzerland, because it would be in German, and I don't understand that well enough to be able to understand what's going on in the course. All the books I have bought are in English.

Hopefully, I won't need to do any practical work, seeing as I am not going to take any exams or anything. Cause I really don't want to blow up my house!!! :D

I realize that I don't need really in-depth knowledge of everything, but I do need to have a knowledge which will give me a basis for intuition in changing glazes this way or that, right? (I work well with basic knowledge and then using intuition based on that to figure out problems.)

I love that likening to a recipe! They are, after all, called glaze _recipes_. Viewing them as cakes or such will probably be very helpful to me when I get to mixing them.

Hmmmm - yeah - and I wonder if the physics side of it might have something to do with my bubble-problems (see other post).

Marianne

I so agree with you about old hardback books! Sometimes, I just open one of my older gems and sniff it, yaknow? Not often, though - someone might see me and think I have something other than paper in there! ;-D

Marianne

Hey David :-)

Dewitt has a chemistry background and found this a bit heavy going, so I think I will just save the information for later use.

But thank you for your input! I might get to the stage where I can read that book and understand bits of it! ;-)

Marianne

- snip loooong list of wonderful links and suggestions -

I also appreciate this room because it is quiet. As you might have noticed, I don't stop in very often these days, so the fewer things to catch up with, the better. Also, because it is a newsgroup, I can mark threads to ignore or follow, and I can view only new posts. That way, it is wayyyy simpler to get caught up with what interests me.

I am firing the glazes to the temperature ranges required by the manufacturer, so the problem doesn't lie there. I've added a little "ps" to my bubbling post, as I had a thought that aluminium might cause the problem - or at least make it worse.

I have also talked with my clay/glaze supplier, and have tried his suggestions without luck. But I had a couple of pots a couple of years ago that also bubbled badly - and he refired them at a slightly higher temperature and they turned out wayyyy better. I try the same here, and I have no luck - so it could also be something with my kiln - maybe it is too small so that the circulation is bad? I dunno. I'm running out of ideas and getting more and more pretty pieces that are impossible to use :-(

Hope you are well from that flu you had and happily jumping around doing your things again!

Marianne

The best source for this sort of information that I know of comes from Orton, who manufacture the cones most USA potters use. If you go to this page

'll find Wall Charts on the right side of the page. These are inPDF format for you to print out. By Googling for "Orton Cone Celsius"I found is a browser-friendly version. Note that you must pay careful attention to heating rate when you use these cone-to-Celsius conversions. There is a column for the degrees per hour for the last 90-120 minutes of firing (or whatever your chart says). You'll notice that for any given cone, the corresponding temperature is lower for the slower heating rates, since there is more time for the heat to work on the clay.

I tend to use the 15C/hour rate, occasionally 60C/hr. I haven't looked at the latest Orton chart, but the one from nmclay above doesn't have a 15C/hour rate, just 60 and 150. If your kiln is topping out near the cone temperature, the heating rate will be much slower than 60... and in fact a slow rate is probably what you want anyway, if your goal is to avoid bubbling. So if the wall chart on the Orton site no longer has this rate, let me know and I will see if I still have an old file around.

Sorry, what I meant to imply is that it's probably not reasonable to expect to be able to look at a recipe and predict all its fired properties. It's worthwhile to develop an intuition of the "character" of each of the players, so that you'll know which ones to add more or less of when you want to change a recipe. The books are good for that. But it isn't really very much like "chemistry", in the sense that you don't find precise formulas like you might for a standard compound. In pottery we are dealing with *mixtures*, and we are interested in melting points (among other things). These don't come down to neat answers; instead the best you can hope for is eutectic melting graphs for a couple of components, which are pretty useless when you have many more than that. So we use the Unity Formula instead, which is numerical but it's more like a starting point for you to make adjustments from.

Best regards,

Bob Masta DAQARTA v3.50 Data AcQuisition And Real-Time Analysis

Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!

Sorry about top posting but I just don't buy that the other is more polite - if you haven't kept up, the old message is there for reference - otherwise why should you have to read it all to get to where you are going... Sorry about the rant but I have never understood the etiquette of bottom posting (I'm not referring to your proper behaviour by the by but my improper behavior - so I'm not ranting at you but defending myself).

I'm all over the flu - just living with the lack of air from asthma due to allergies (I'm really hoping it snows soon). Which makes me cranky - which explains the above silly rant. Thanks for remembering and thinking of me.

How does this glaze behave over or under other glazes? If they have sold you a glaze that is not maturing at the temperature they claim then bad on them (you should not have to fire higher than what they say it fires to). Is there a reason you are sticking with this glaze when it is behaving badly? The reason I ask these questions is that depending on why you are keeping this glaze and how it behaves with other glazes - there might be short term fixes.

Donna

P.S. I also like this room better because you are more likely to get a response (even if it is maybe more likely not to be corrected if it is wrong) and you can easily follow threads. I hate the inability to keep a thread together in Clayart. I posted your original question there and never did get a response. There is quite a bit of chatter though on all sorts of odds and ends I would never want to follow. Still, if you can at least do searches there, I think you would find it useful and that is where you would pick up the pearls by the experts. As it turns out really - most questions you would ever ask have already been asked and the ones that haven't are usually impossible to answer.

I have my Clayart email, as well as most my other email lists, sent to my gmail (google email) account. gmail automatically threads conversations. I simply filter my different email lists into separate folders. Oh, and gmail is free.

If anyone wants an invitation to get a gmail account, send my private email and I'll send you one. Posting such a request to the group, however, will get you scorn and ridicule. :-)

deg

I'm real confused (again) - you just go to goggle to get a gmail account don't you? Or are you referring to belonging to a group?

I tried having clayart emailed to me and was soon so overwhelmed with emails that I just gave up on it. Clayart does have some mapping to threads but they are frequently broken off depending on how people answer the posts. So you can have dozens of threads with the exact same title. Since Clayart is a list and not a group it behaves in a very different and archaic way than what you now find in newsgroups.

It used to be you had to receive an invitation to get a Google mail account (phased introduction of a beta product or viral marketing?) but now you can just go there and sign up.

Didn't know that. They still have an "send invite" function on my gmail page. It was probably viral marketing, but it worked really well!

deg

I finally gave up on Clayart last year, even though I was getting the Digest format just to avoid the above-mentioned Email blizzard. The problem is (was?) that the moderator just didn't have control of the Listserv, and apparently nobody was really administering it who knew what they were doing.

The kicker for me was that Clayart insisted on posting all messages to the archives, with your Email address clearly visible to bots. So I was getting several dozen spams a day just due to that. (I had a separate account for Clayart, never used for anything else, so I knew that's where they came from.) Other lists "munge" the addresses in the archives, to make bot harvesting tougher. (Munging is where you replace " snipped-for-privacy@MyHost.com" with something like "MyNameMyHostcom", which any human can figure out but is tougher for a bot.)

(As an aside, the moderator also was getting hit with tons of spam to the list itself. This is an easy problem for a Listserv administrator to fix, but the moderator couldn't do it and didn't want to bother the (nominal) administrator that was hosting the list for free. So he spent hours each day dealing with it himself.)

Anyway, when my workload got high enough that I was no longer willing to put up with the spam, or with wading through personal and philosophical monologues to get to clay stuff, I let it go. I guess I'll give it another look if and when things calm down... maybe they will have gotten the administration squared away by then!

Apologies for the diatribe...

Bob Masta DAQARTA v3.50 Data AcQuisition And Real-Time Analysis

Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!

Bob and all: Clayart is indeed going through some growing pains. It is "owned" by the American Ceramic Society, and is being moderated by volunteers who have absolutely NO control over what ACerS chooses to do or not do. in that, Bob is right. The moderators have little control, all they can do is approve or disapprove posts to the list make minor changes etc.. The software being used is also completely outdated. Clayart is being run on a server using Listserv software version 1.8, while the newest version is 18.0. That should tell you something.

In addition, until very recently, ACerS was changing their IT staff more often than I change socks. Here today, POOF!, gone tomorrow...no one seemed to know what the administration password is, etc. But, things are looking up. There are some very dedicated experienced volunteers working on the IT problems now, as well as new staff at ACerS, and some progress is being made. It will get straightened out.

Remember that Clayart is a group of potters, around 3000 of us, worldwide. (Our latest member is a ceramic studio/center in Cambodia, which is amazing to me.) And it's free, so I tend to overlook a lot of the problems in exchange for the information and world view that I receive. Yes, there is a LOT of e-mail, (3000 people have a tendency to do that ) and so I have learned to delete threads in which I am not interested. With Clayart, your delete key is your friend . Still, it is worth joining Clayart for the information contained in the archives alone, which date back over 12 years now. If you can think of a ceramic problem, chances are you will find the answer in the archives. If not, post the question to the list, and you'll have your answer.

I guess I don't have to say that I'm an enthusiastic supporter. One of the things for which I will always appreciate Clayart is the presence of its memebers at NCECA's annual conference (National Council on Education for the Ceramic Arts). The conference is held yearly, a different city each year (next March it will be in Pittsburgh Pennsylvania). Of the 6000 attendees for the last conference held in Louisville Kentucky, over 2500 were members of Clayart. We had our own hotel (which sold out) for that conference and we are also getting our own hotel (The Omni William Penn) for this one. That says something about the power of numbers (of crazy potters ). Not only do you get to learn from some of the largest "names" in ceramics online with Clayart, you actually get to go meet them, share meals, go out on the town, learn, etc.. It's more a big "family". A big, talkative family. And I am thankful to be a part of it.

Best, Wayne Seidl Vice President, Potters Council of the American Ceramic Society 2007-2008