Chemistry basics for potters?

-snip-

Glad you are feeling better. If I get any snow over here in Zurich, I will HAPPILY send it your way! ;-)

All the glazes I use behave very well normally. It is just with this "beautifier" on top that I get the bubbles. It may be that I am putting too much on. I am currently making up a bunch of tiles that I will criss-cross with different thicknesses of glaze and beautifier to have a more accurate example of what happens with the thicknesses/combinations.

Marianne

I absolutely agree with you that clayart is a good resource. The trouble is that it is rather messy to search and you get a lot of things you don't want. Partly my fault for not putting in the parameters better, but still. Also, this bubble problem is very specific, so I did want a dialogue - and I am not about to post over on clayart - got too many places to post already in different subjects.

But I thank you for posting there for me, and am sorry nobody gave any feedback.

Marianne

Back step.... I'm sorry, I totally misunderstood what you were doing. What is a beautifiers? That completely changes things. When glazes are too thick you will get bubbling - so if you are layering your glazes and then putting this last layer on rather thickly I would not be surprised to see bubbles. Have you taken a needling tool to check how thick your glazes are (the final product)?

Spelling correction - and - have you tried thinning the beautifier down quite a bit and doing overlapping brush strokes so you get different thicknesses of the beautifier to test the application?

Donna

Okay. I paint all my glazes on and have them in little pots ready for that purpose. Dip-glazes take way more space than I have available!

The beautifier, which only works with stoneware 1250 C glazes is an addition. It is white in color and quite liquid. If I thin it down, the effect is less as well. This stuff makes the glazes run if it is put on "too" thick and gives wonderful results.

Never heard of checking final thickness of glazes. Any idea where I can get hold of that tool=

Hugs

Marianne

Ok, another idea - try firing the piece once with the first glaze. Then paint on the 'beautifier' (that is just such a weird term) and fire again. See what happens in that case.

Put a scatch in the glaze with your nail. Also your glazes will thicken over time and need to be thinned. How much glaze do you have and do you have a scale?

Good idea. Means firing the piece 3 times in all, though, instead of just twice.

Maybe I should take hubby up on his offer of buying me a bigger kiln!

Marianne

I do have to add a little water to them now and then, for sure.

I have close to 40 high-fire glazes and around 12 low-fire glazes - plus some underglazes colors.

I have an old kitchen scale that I use to weigh my clay before I dump it on the wheel. It weighs up to 2 kilos.

Happy weekend!

Marianne

You so DON'T sound like the amateur you pretend to be... :)

Donna

Oops - meant to say - I would only do that as a test to try to track down what is going on. Go to clayart

and do a search for blistering or blisters in Title and Body - many ideas are there.

LOL! Thank you!

I AM an amateur, though. I have sold only one piece (at a students' exhibition my teacher held), although I do hope to start selling some stuff on Ebay soon.

I have only been working with clay seriously for about 5 years. Compared to you guys, I am a baby. And I so greatly appreciate all the input I get from y'all!

Marianne

Wow - almost too many ideas! Hehe!

The consensus seems to be that iron can be a problem. I don't think my clay has iron in it, as it is grey unfired and almost white fired. BUT the glaze that is my biggest problem is red when unfired, so I am suspecting it might have iron in it. Possibly a sollution would be to ignore the extra power required and leave the bottom and top (lid) holes open through the whole firing in order to provide enough oxygen?

Marianne