I need to do some small bends for an old fixture. Can anyone recommend a good method of acheiving that oldtime acid washed matte white look you see on schoolhouse type fixtures from the 30's and 40's? Should I just sandblast them, or use a wash? Anyone try over-firing to achieve this effect? Do I bend first and then wash?
We bend a fair number of cabinet sliders, often replacements with sandblasts. Find it a lot easier to blast first, then bend. Only temps around 610oC (1140oF) of so is needed for float we deal with.
The few times I've worked with stained glass, notice it goes much faster, or do about 10 - 15oC (50 - 60oF) lower.
Mild steel or zinc anneal moulds, no kiln wash required.
Please expand on this last sentence,,, thanks!
Just have steel sheet bent to radius / shape etc, and provided you don't go over the temp range concerned, it doesn't need any further treatment. Steel moulds can be shape by numerous means, tack welding in fins, or using an elaborate system that enables mould skins to be re-shaped to slightly different radii, even a turnbuckle setup can be fashioned to shape a skin.
The black mild steel will flake etc, especially on the first cook, but after that, a quick rub with 120 grit or so sandpaper will take any scale off, and bring it up nicely to use. I have mould skins that are still fine with a quick rub, that have been in use over 15 years and have be through hundreds of cooks. An occasional hit with a sander if they get too rusty etc. Never had kiln wash near them.
Doesn't matter if it has a few pits / rust / even small dings, as long as you cook for minimal time the glass won't take on any marks etc. Say a standard cabinet radius bend (3' high x 16" girth or so), I'll cook for around 15 - 20 mins @ 610c or so.
Zinc anneal sheet doesn't flake at all (usually !), and last a lot longer. Doesn't cost much more, so all my moulds are made of za now.
If I have a bend that needs a fair amount of time (180 degree bends / thicker glass J bends, etc), I'll use thinfire. Mainly to stop heat pitting, still won't stick at those temps. Don't bother pre-firing, I just take of the milky scum in the centre with Hydro acid and quad 0 steel wool, takes just a few minutes.
Oh, and I have no problems at all bending over or into these moulds. If you bend over, cut the girth oversize to pull it down onto the mould, trim later. Into a mould you can cut to size as it bends fro the outside edges to the centre (I like this way for furniture bends with polished edges, glass also sits on the steel for less time . . . oh yeah, I use stainless steel for the high grade bending into a mould).
Cheers
Use "ds ground" to start with, it has a softer finish than the stuff we end up with sandblasting, and doesn't change much when bent either. Had good luck with it myself.
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