I've had my Scutt Firebox 8 for a few weeks and have had mixed success. It has been pretty successful using pendant moulds with some excellent results after working out how to get rid of spiking (using fine or powder frit solves the problem), so I've bought more powders and millefiore to experiment further.
However, my first attempt at a coaster was an unmitigated disaster. I used the sample coaster kit fron Warm Glass and put it on the auto fast full fuse on the programmer. The coaster stuck to the kiln shelf and when released was like a shattered glass. My assumption is that as it stuck to the shelf it carried on contacting which set up massive stresses which caused it to crack in a honeycomb fashion, each polygon being a few millimetres in diameter with kiln wash stuck to bottom layer. Unfortunately I forgot to take photos.
I've re-kiln washed the shelf (on the other side) and am trying again today while I'm out.
Basically, am I right that not having enough fresh kiln wash was the problem?
I always use Thinfire paper under coasters etc. It leaves a smooth bottom on the coasters and prevents them sticking to the shelf.
Nick
I use Spectrum Papyros paper, with care you can get 2 firings from a sheet, and not had a failure yet.
I usually can get a few firings - up to 5 or 6 depending on the firings - before I clean and redo the wash on shelves. The one time I had something break because it had stuck to a shelf it had only stuck at one point and broke cleanly in two. Shattering sounds like a compatibility issue but that should not be a problem if you used a kit. I did have a problem with some pieces having batt wash stuck to them (but they didn't shatter as a result) and that is what really made me learn how to set my own programs to be a bit lower that the preset ones.
Thanks for the comments. Definitely not a comparability issue as none of the others in the kit have done the same pattern with the remaining 3 coasters. I had only used the kiln wash for one fusing, but it had been in the kiln for about 6 fusings of pendants in moulds, so was a bit old.
However...
The next 3 coasters came out OK, but I experimented with the tekta on top and underneath. Tekta underneath came out slightly uneven on top, but two I did with it on the top had an interesting outcome. Basically the white glass stuck to the kiln wash and when I took it out a perfect triangle of wash came off the shelf. This happened twice in exactly the same way, with nothing sticking to the other pieces. I'll take photos and see if I can work out how to post them here.
Some colours do stick more than others but lower temps might help. What is the programme? I use kiln wash or fibre paper and the only time something has cracked (which was single crack all the way across, not honeycomb) the smooth edges on the crack indicated that it had cracked on the ramp up. Very close inspection indicated that frit i had used was contaminated with a single metal filing.
This was definite sharp edges, almost like when you drop a glass tumbler and the cracks went clearly through both layers. I'm going get some thin fire on my next order so the problem won't re-occur.
Programme was the preset one on the kiln programmer, fast full fuse. It works for fusing Bullseye pretty well and I think I've seen something before about Kiln wash sticking to some colours but not others.
Opals always stick to kiln wash, in my experience (others might disagree).
I found that spraying the (kiln washed) kiln shelf with MR-97 worked really well. I used to re spray thinly every five or six firings. The finish on the bottom of the flat items was the smoothest I've ever had, much, much smoother than thin fire or papyros, and opals released cleanly. It's expensive, but I liked the finish better, and it was faster for making frit balls. You have to be careful to avoid scratches in the base layer of kiln wash, because the glass will sink into them and you'll have lumps on the bottoms (*snigger*) of your pieces.
Quick update.
No sticking since I started using thin fire, and it's about 8p a coaster and 15p for a 15cm plate so not expensive compared to the glass.
Only one breakage since then, on a slump. I must have knocked it slightly off the mould so it draped over the sides, then cracked as it cooled and contracted. I tack fused it flat and it looks OK, but will need a few embellishments before it's finished.
sounds like you are making progress!