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the tin side of float will resist paint more than the air side.

Dear all, thanks for the info! Thanks for the acetone tip, Charlie.

A follow up on the firing/ whiting issue, where after firing my glass was ghosting/ picking up whiting on the posterior side. I did a new kiln test, after first cooking the whiting in my home oven for a few hours to remove moisture, and then firing in an electric glass kiln. I made sure the whiting was flatter this time. There was no ghosting. I used a different type of whiting, Bologna chalk. And I also tried whiting and plaster of paris mixed together, as per Patrick Reyntiens' book. This worked fine too, didnt notice much difference between that and whiting only.

Cheers, Sasha

When do we get to see pictures Sasha?

Williams and Byrne in the UK have a website on glass painting - This video is one of many

Preparing a whiting bed for glass


http://www.realglasspainting.com/staine ... kiln-tray/

Hi Don, only fired some tracing so far, so not much to see yet! Its a fairly slow project, but I'll put something up once I've done a bit of matting! Cheers, Sasha

Hi there, a new firing question if I may! Well, after being a happier with my 2nd firing, I showed it to a professional glass painter here in Germany who said it was overfired, that the glass had warped, gained too much texture. This also explains why the tonal loss in the lines was roughly 40%. But as they use a different brand of paint/kiln, they couldnt help me specifically with changing the schedule.

this was the schedule
Segment 1. 300C per hour to 675C. Soak 5 mins.
Segment 2. Maximum Speed down to 560C. Soak 5 mins.
Segment 3. 10C per hour to 530C. (No Soak) Turn Off.

I'm wondering how to adapt the firing schedule next time, to try to prevent any chance of overfiring. I assume the first step is to go down to the recommended minimum of 650C for Reusche paints?

After that, I'm wondering, in terms of what actually warps the glass, is it more important to adjust the ramp up the firing temperature, or the annealing range, or both? I assume the idea would be to make them both faster?

Many thanks! Sasha

Over firing is a factor of heat work. Heat work is a factor of both time and temperature. It is effected by the mass inside your kiln, which is different for brick and fiber kilns. This difference means that somebody else's schedule may not work the same for you.

vitreous colors are designed to soften and gloss all over the temperature range. You need to fire according to the colors you are using. There are colors designed to paint on glassware and not slump the glass, and there are colors designed for decorating pottery. The powders look identical, but behave quite differently. A lot has to do with how cadmium and selenium oxidize. As you fire hotter these chemicals behave differently and the formulas are designed to take this in to account.

If you really want to know the point at which glass will begin to distort in your kiln, you can do a slump test. Cut a strip of glass about 1" wide and 12" long. Cantilever it between 2 firebricks. Then place another firebrick just past the end, so you can see when the glass begins to move. Fire the kiln to a temperature beneath where you think the glass will start to move and hold for a half hour. Then raise the temp 5ºF or 3ºC and hold for another half hour. Note the temperature when the glass starts to move. In the ºF world, you can anneal soak 100ºF beneath the temp where the glass started to move.

Sashaziv wrote:Hi there, a new firing question if I may! Well, after being a happier with my 2nd firing, I showed it to a professional glass painter here in Germany who said it was overfired, that the glass had warped, gained too much texture. This also explains why the tonal loss in the lines was roughly 40%. But as they use a different brand of paint/kiln, they couldnt help me specifically with changing the schedule.

this was the schedule
Segment 1. 300C per hour to 675C. Soak 5 mins.
Segment 2. Maximum Speed down to 560C. Soak 5 mins.
Segment 3. 10C per hour to 530C. (No Soak) Turn Off.

I'm wondering how to adapt the firing schedule next time, to try to prevent any chance of overfiring. I assume the first step is to go down to the recommended minimum of 650C for Reusche paints?

After that, I'm wondering, in terms of what actually warps the glass, is it more important to adjust the ramp up the firing temperature, or the annealing range, or both? I assume the idea would be to make them both faster?

Many thanks! Sasha

The ramp up seems pretty tame and the annealing descent wouldn't contribute as much to warping as the high end temps. Maybe remove the hold time at 675°C. Start adding it back a minute at a time in tests if the paint surface isn't as glossy as you like and if you haven't distorted the glass too much.

Dear Bert and Don, thanks very much for the replies, very helpful! I'll try to test the kiln, and change the schedule.

The pieces have very thin line work. I'm wondering about the tonal loss issue too. I'm sure it's always variable, but typically for you, would tonal loss increase with the temperature/ soak time? Might there be a difference in the amount of tonal loss between a 5 min soak at 650C, and for example at 675C? Or might it more to do with the soak time than the temp?

And, out of interest, if you had a piece with ultra-thin lines, assuming the glossiness is not so important, would you go for a lower temp/ shorter soak time to prevent tonal loss?

Many thanks! Sasha

I don't have those answers. I don't think about tonal loss much, particularly on lines. Makes me wonder about your paint and its application. I really think systematic tests are the way to go to figure it out. Takes time I know. I have a little test kiln that I spent $600 on. I love it and use it a lot for making little samples. I have a lot of little samples. I've been telling my wife she'd really enjoy a second little kiln for her birthday this summer.

Thanks Don, yes, I guess, probably the painting had something to do with it too! I guess tests are the answer indeed.

By the way, at a glass shop I went to recently, they fire their painted glass in a long and wide electric kiln with a floor lined with heat resistant padding that looks like white foam. Apparently it doesn't leave any texture on the glass, at least not until fusing temperatures. I couldn't quite understand what the material was, as they explained in fast German, and I'm not exactly fluent! Any ideas what it might be? (I guess I could take a photo next time I'm there!)

Cheers, Sasha

Hi all, well I've had a few delays, but I finally finished my first piece recently. It's a copy of the "Game of Quintaine" roundel in the Met's cloisters in NYC. So, as promised to Don, here it is! I'd be interested what you all think. Cheers, Sasha

I think you did a lovely job. Your glass takes stain well.

You got the olde English thing just fine.

Sasha, your reproduction looks very professional! I put the Met's original beside yours on the screen:

http://www.metmuseum.org/collection/the ... rch/469853

Did you use float, as you mentioned earlier? I notice, too, that earlier you'd asked about doing your fine lines last. I think that would cause a problem with any enamels or silver stain as you'd have to fire your fine tracing lines, painted with stainer, at the higher temperature which would probably fry any enamel or silver stain already applied. Jen

Dear all, thanks very much for your kind comments, really appreciate it! I'm really happy with the piece - it was a wedding present for my cousin, who was very happy indeed with it.

Re your questions Jen, yes it's on float glass. I used yellow & orange silver stain mixed with copper sulphate, as I don't have any amber intense stain, and the original is quite amber-ish. Re the fine lines, I meant the lines as a last painting layer before the silver stain, so metalling of the stain etc. wouldn't be an issue, as the stain would be fired next.

One thing though - the reusche de401 black came out quite greenish on several pieces. I'm wondering if there are more neutral blacks available? (like lamp black) I'm actually going to try some keracolor paints next, they have a few interesting blacks.

Many thanks, regards, Sasha