Those look like bloats to me, which are bubbles in the clay, usually due to over firing. You can see that there a very small, smooth bumps that haven't come through to the surface quite yet, as well as the big bumps. Could also be a bad batch of clay, which is what I'm betting on. Use some cones to rule out the over firing possibility, though. In my experience, digital kilns tend to under fire as the thermocouple ages, not over fire, but it's definitely a possibility. However if it was truly over firing enough to cause bloating, I would expect your glaze would also show some extra fluidity, which you haven't mentioned. If you've still got the boxes that the clay came in, check to see if they're all from the same batch. Also try a couple of pots with another glaze to see if it still happens. If the kiln is not over firing, call your clay supplier and let them know what's going on. They'll want to know the batch numbers.
5 years ago I was selling mugs for $30. 3 years ago I dropped the price to $26, and I now sell a lot more mugs. I can make them pretty quickly, but I do have other forms that are much more profitable. For instance, I get $36 for oil bottles, which take only about 30 seconds longer to throw, but take 1/3 as long to trim, and a little longer to glaze. All said and done they are still faster than mugs, though, and people don't blink at $36. I sell more of them than any other form. It seems like the more functional something is, and the more they will use it, the less they are willing to pay. I can get $100 for a vase, but put a spout and handle on it for a pitcher and I can only get $70.
Things are definitely different in Australia and Europe than in the US. A good kiln manufacturer should be able to get you whatever you need, though.
1, 2, or 3 phase power are all the same when it comes to firing costs. A certain number of watts are needed to heat up the kiln. Regardless of the amperage or number of wires being used, the watts will be the same, and watts (kilowatt hours) are what you pay for. So a 3 phase kiln will not cost you any less to fire than a single phase kiln. If you've got 3 phase, get a 3 phase kiln. If you've got single phase, get a single phase kiln. It's not worth the cost to try and change things.
A Skutt 1027 will pull 48 amps, and will need a 60 amp breaker. Get an electrician in to make sure your breaker panel can handle it. As John said, the cost of running the electrical lines can cost more than the kiln. You don't want any surprises.
Make sure any kiln you buy is set up for 240 volts, single phase, because that is what you have for service in your home. 220 is a generic term. Kilns are either 208 or 240 volts, and single or 3 phase. The kiln must be the same as your house or it will not work properly.
Neil, what are the advantags of paying for 3 phase? I guess my queston is what are the limits on a single phase kiln..Size?
No electrician here.
I think the kiln I have is 2 phase but an electrician directly wired it so it works on my single phase power???
Can you elaborate?
You either have a single phase kiln or a 3 phase kiln. 2 phase systems date back to the early 1900's and are rarely seen any more. Direct wiring does not affect the phase. Single phase uses 2 hot wires, 3 phase is 3 hots. Most kilns do not use a neutral wire, just a ground, so single phase kilns have a 3 prong plug, and 3 phase kilns have 4 prongs. Some smaller kilns use a neutral with single phase, so a 4 prong plug, but you do't see those much.
You can't get 3 phase at your house in most towns. It's for commercial use. In homes, the service is 240 volts, single phase, unless you're in a converted commercial building in which case it's possible that you have 208 volt service, but I've personally never seen that. Commercial spaces can be 240 or 208 volt, single or 3 phase. Most newer commercial spaces are 208 volt 3 phase. The benefit of 3 phase is that you can pull the same wattage on lower amperage, so you can get more stuff running off a breaker panel than at single phase. Since commercial spaces run a lot more machinery than your average household, it's a very handy thing to have. So for instance a kiln that pulls 48 amps on single phase will only pull 27.7 amps at 3 phase, since the power is distributed over 3 wires instead of 2. So you could run 3 kilns on 100 amps instead of 2.
A thin lip is more comfortable to drink from. It's easier to get your lips on, and the liquid jumps off the lip better than a thick lip. However, it should still be rounded and smooth- it's just a smaller radius than a thick lip. I find the thick lip on #2 to be uncomfortable, and our brains see that thickness as being the thickness of the entire pot, which makes it look heavy. The problem with #3 is that it is not smooth and rounded, and flares out too much.
I have participated in many art fairs where the booth across from me was a potter who makes less than acceptable work and sells it for a third of the price of mine. I have sat there in my booth for hours and hours watching the line of people wanting to buy their $8 mugs and $12 baking dishes. At first it drove me nuts and made me angry. Now I just ignore it and focus on what I'm doing. We will never be able to educate the entire buying public on what makes a pot good or bad, nor convince every potter to take a few more classes. It is what it is, as frustrating as that can be.
Every glaze does not fit every clay. Not even close. You've either got to do a lot of testing of clay and glazes to find matches that work, or you can alter the glaze. Increasing the silica in the clay will reduce crazing. Take 200 grams of powdered glaze and add 3% silica (6 grams) to it. Blend, dip a tile, add another 3%, blend, dip a tile, and repeat until you've reached 15% silica. It's not super exact in the higher amounts, but it will get you close. Once fired you can see which tile is best and do another round of more precise tests to get it perfect.
I think the bigger question is: Are you insured if your booth blows over and destroys some of your neighbor's work, or if one of your pots breaks during use and someone gets injured as a result? For potters, the cost of materials is generally insignificant compared to the cost of labor. All the pots I take to a show have a materials value that is less than the cost of an insurance deductible. To break it down simply, I can probably fit around 300 mugs in my booth display (not that I only have mugs in my booth, but it gives us a good baseline). With porcelain that costs me about 55 cents per pound, that's $206 worth of clay, plus glazes which might add another $30. It's not enough to worry about. Compare that with a $100,000 lawsuit because a handle broke off your mug and someone got scalded by hot coffee, and you get the picture. You should be protecting yourself against liability to others.
Oil based or polymer clays do not feel the same as real clay, and won't teach you anything about proper construction techniques and such. You can get clay for 30 cents a pound or less. Just get the real stuff and go for it.
If you mix two clay bodies from the same firing range, then they will be fine. Many clay manufacturers sell half-and-half bodies, a porcelain/stoneware blend. They are generally very nice. Start mixing ranges and you'll have to do some testing. As for mixing slips, the same rules would apply, however I'm thinking that the viscosity of the slip could possibly be affected when they are mixed together. Just a guess. It's worth a try.
I am open to haggling on my more expensive pieces, like those that are $200 or more. They really don't take much more effort to produce than the $150 pieces. I also give discounts to students, because I remember how frustrating it was to never have enough money to buy nice pots when I was in college. If someone buys 3 or more of something and they ask for a discount, then I will usually give it to them, but rarely for just one piece. If someone is paying cash and comes up a couple dollars short, then so be it. All of the prices we set are totally arbitrary and open to adjustment. We hope people think it's a fair price and are willing to pay it. It's not like buying wholesale and marking it up 30%. I'm always adjusting prices because the market is a mess right now and it's hard to know what people are willing to spend. I won't give a discount to someone just because they're cheap, but I'm open to the idea that my prices might not be set correctly for the current market.
That is the kind of learning we should be focusing on here, not picking holes in it. Perhaps I am misunderstanding, but I feel like you are spending a lot of time here trying to dismiss, distort or otherwise undermine this testing technique whlle the rest of us are trying to learn about it and share information and images and experiences and make a POSITIVE contribution which benefits all.
Of course you can tweak or alter Currie's technique to test anything you want, but once you change it enough it is not really a Currie test anymore, but probably some kind of quadraxail, triaxial or or other method, or your own concoction. No problem with that, but there is already a lot going on in a standard Currie grid. I would suggest that anyone looking to extract maximum value from this technique concentrate on learning everythying it has to offer first, before making major changes.
I think everyone understands your preference for vertical test tiles. As I have said, I regularly use vertical test tiles myself for all sorts of things and I am sure many others here are the same. However, like Currie tiles. they are only one of the arrows in the quiver, and there is no need for anyone to have to choose one over the other. They all have their place. I think the reason many people are following this thread is because most people ARE NOT familiar with the Currie technique and how it is done, but would be interested in knowing more about it and maybe even joining in the discussion. So can we please focus on Currie tiles and what they CAN offer rather than what they cannot?
I am in no way trying to dismiss this method. I apologize if you feel that way. High Bridge noted that he was having different results on his flat tiles vs his vertical tiles, and I made a comment pertaining to that issue. But when you responded that you "haven't seen much difference" between flat and vertical tiles, I felt that will lead people who are not very experienced with glaze testing to think that is the norm, which I feel it is not. And that is my point, nothing more. You asked me to give examples supporting that point, which I did. To then claim those examples do not pertain to the definition of a Currie test does not make them invalid. Glazes do behave very differently depending on whether or not they are fired vertically or flat, and I feel flat tiles are very limiting in how much information they give about a glaze.
I studied Curries method in grad school, and I have used it off on on for the past 20 years, and I think it is very worthwhile. I apologize if you got any other impression form my comments. But even if I did not think it was worthwhile, or if I had ideas on how it could be improved (which I do), this is a public forum and it is important that anyone be able to add to the conversation, whether it fits your definition of what you think the thread should be or not.