I work in etched glass, not stained. But I like to work with odd shapes, so I've considered a glass grinder, and I have a few questions.
I'm curious as to how badly the edge is chipped after its been ground. I know the stained glass crowd puts came or foil around the edge, so it isn't an issue. But for me, it might be. Can someone send me a close-up pic of the edge of a piece of glass after it's been ground so I can see the finish? Also, it looks to me that most grinding heads are 3/4 to an inch tall. Would they'd work on 3/8" or 1/2" glass? Seems like it'd be OK, but wonder if anyone out there has had experience with this?
I work with fused glass, so I have the same grinding question. The normal coarse head leaves a very dull scraped durfsce. You can buy a fine head to smooth after that. Diamond hand pads are good for finish. You need a series, like
220, 400 and 600 grits. After that you have a surfade like sandblasted. further finsih requires polishing. HAve you consider fire polishing?
Simple answer is 'it varies' - seems to depend on the type of glass. Some glass will chip at the edges, some doesn't. Plain, clear, machine-made float glass is usually OK - the more 'fancy' the glass gets the more liable it seems to be to get chipped...
My experience is that, wherever possible, it's best to cut rather than grind (quicker!). However, when I'm doing foiled work, I always run round the edge of the cut glass with the grinder, just to take off any sharp edges that would otherwise damage the foil (or me!)
There are different grit grades of grinding head available - I tend to use 100 grade most of the time - and usually a 3/4" head. If you want to take the time, then you can use heads with finer grit - I sometimes use a 600-grade head, but not very often.
I do quite a lot of work with mirrored glass - and have just bought a specific mirror-grinding head - which grinds both top and bottom surface of the glass at the same time. I'm still experimenting with it - but it does seem to reduce the problem of chipping the mirror coating off the glass - and leaves a reasonable semi-rounded edge on the glass. Aanraku do them. I'd imagine that, using a combination of the mirror-grinder head and a conventional coarse head you could create an acceptable finish on the edges of your etched glass work..
The mirror-grinder head does tend to 'grab' the glass and try to throw it across the workshop - so practice on some scrap first!
The 'standard' grinder head can be moved & locked up & down the grinder spindle - so you can start out with the head only just showing above the grinder table, and then, once that 3mm strip of diamonds has gone dull, you can re-set the position so a fresh set of diamonds is exposed - so you can get mugh longer life from a single grinder head...
If you want some photos then I'll send you some after the weekend (busy selling at the open-air markets this weekend - weather permitting.
Thanks to all who responded to my post. They were quite helpful.
I am using a sandblaster. And I'm not really looking for a purfectly polished edge. In fact, I've used the blaster to finish the edge of the glass a time or two. Seems like a grinder with a couple of different heads might do the trick.
Lauri brought up fire polishing. I'm wondering how much fire are we talking about. I'm guessing more than my propane torch can supply.
A point source of heat like a torch will break your glass. In order to fire polish, you need the entire piece of to be at least to the strain point, and preferably at or above the anneal point (~950-1000°F). Then you can apply a torch to the edge to fire polish without worrying about thermal shock, ?T's, or internal stresses. IOW, fire polishing is generally done in a kiln. For your application, I'd think you'd want to fire polish before doing any carving/etching.
Understood. And since I won't be buying a kiln anytime soon, I'll stick to grinding.
Again, thanks to all.
"Fire polishing" is a term used to refer to a method of producing a smooth edge by heating the glass in a kiln to a temperature high enough for the glass edge to soften and smooth out. Clear float glass would require heating to 1350F and holding at that temperature for 6 to 10 minutes (depending on how smooth it was ground before going into the kiln).
As was mentioned, it is essential the glass be heated uniformly. It it isn't heated uniformly, it will crack. Can't do it with a torch unless the torch is big enough to fan flame over the entire glass surface.
Adrian wrote in news: snipped-for-privacy@mid.individual.net:
What I've found in grinding clear textured glass and colroed glass up to
3/8" is taht you have to be very sure to keep the glass flat on the grinder table, and apply a smooth, even pressure while grinding.
I'm not a pro, but from all I've heard and read, the reason for the grinding is to provide "tooth" to improve the adhesion of teh sticky side of the foil becasue, if the glass is smooth, you lose structural integrity - is that incorrect?
I took a kiln-worked glass course and the instructor used the diamond-sponges to finish edges. The grinder is good for removing larger amounts, but yeah, you're right, the OP should cut as close as possible to the intended outline of the item, since that will reduce wear on the grinder head (since it won't have to be used as much).
snipped-for-privacy@debrady.com wrote in news:e68a951f-5d80-4dfe-b5a0- snipped-for-privacy@b2g2000prf.googlegroups.com:
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Oh! Ok, I didn't know that. I wonder why peopel say grinding is to make it stick better - maybe teh original idea was to keep the glass from cutting thorugh the foil, and that got confused with the idea of foil sticking to the glass...? It's not important, I'm just curious.
Ok - that actually solves the problem of what to do when you actually do cut right on the line so to speak, IOW, when teh piece fits almsot perfectly but gets too small when ground - I had the latter happen just recently, and ended up wasting glass by cutting another piece...
No, unfortunately - too many years in apartments leads to a lack of power tools
Foil WILL stick better to a slight rougher surface than a smooth surface. The adhesive on the foil gets embedded into the "rougher" surface and does provide a better grab. However, our resident King Troll Dennis is correct in that the foil is only a platform for the solder to ahere to. Tiffany used bees wax to make his foil stick. If you doing mostly copper foil work, don't spend the money on a wet belt. A Glastar grinder will do just fine.
Chemo the Clown wrote in news:0ec6a2f8-7189-4ef8-be44- snipped-for-privacy@i24g2000prf.googlegroups.com:
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OK, that makes sense, given what I know about adhesives in general.
Right - and when the solder hardens, it provides some support (in addition to the frame). I also bought some "strengthener" (stripping that's heavier than foil, and goes in-between the foiled pieces).
I bought a Gryphon grinder at a good price - it's fine for what I'm doing so far; I'm doing this small-scale, so I can't afford anything too expensive.
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