matte finish

[Patgsc]

How can I get a matte finish on 6mm of fused BE glass? I do not have access to a sandblaster, and after reading a number of posts here as well as Brad's book, I'm afraid I'm still confused. Two questions: how to get a matte finish when that's what I plan to do from the start? And why didn't this work: I fused 2 layers of med. green glass but noticed some flaws along one of the edges when it came out of the kiln. I ground the spots and fire polished going 300 deg/hr to 1100, holding for 10 min. Then I increased the temp to 1140 and held for 1 hr. Finished the firing with the normal annealing schedule, etc. The piece came out with the same glossy surface. Any help would be appreciated.

[Brad Walker]

I ground the spots and fire polished going 300 deg/hr to 1100, holding for 10 min. Then I increased the temp to 1140 and held for 1 hr. Finished the firing with the normal annealing schedule, etc. The piece came out with the same glossy surface.

I'm not sure I understand. If you ground the pieces, you made them dull, not glossy. So I'm not sure what you mean by "the same glossy surface."

Part of the confusion may be that people use the term "fire polishing" to refer to two different kinds of operations. One is firing to achieve a shiny surface, which requires a fire to around 1350F or higher. The other is fire polishing to achieve a matte finish; that requires a lower firing (such as the one you used). But in order for the matte to work, you need to sand blast so that the surface is the same all over. If you don't have a sandblaster, you might be able to do this with a loose silicon carbide grit slurry on float glass, but I've never tried that so can't say for sure.

[Morganica]

Any time you fire the glass, you are softening it (or at least starting to soften it)--the more heat you subject it to, the softer it's going to get, until it relaxes and flows and gets shiny. So heat >>> shiny.

When you fire-polish an abraded (ground) glass surface, you're softening the abrasions. The glass will start out with a matte finish that--if you continue heating--will progress to silky, then satiny, shimmery, then a full-gloss shine. At that point you have fully fire-polished (or melted) the surface back together.

So, basically, you heated it too long. A lot of people who sandblast to a matte finish also fire "polish," but they heat for far less time, just long enough to "set" the surface and make it more resistant to fingerprints/oils.

If you don't have a sandblaster and need an even matte finish to your glass there are a couple of ways to get it. The easiest, probably, is with etching cream sold by most hobby stores. If you're careful with it (it is nasty stuff), you can get some beautiful effects.

The other way is with wet-dry sandpaper and a sponge. It's a bit less messy than a silicon carbide slurry but still takes some elbow grease. Get a pack of about 200-grit wet-dry at the hardware store and a cheap pack of thin kitchen sponges. Cut a piece of sandpaper to fit around the sponge, dip it in water, (wear gloves, this gets hard on your hands after awhile) and start working in circles over the piece, varying direction.The sponge helps push the sandpaper into the glass and increases the cutting action, gives you a beautiful matte finish.

I'd practice on a piece of scrap first, to see which paper/technique gives you the effect you want. You can vary grit sizes and techniques for a lot of different effects.

[Patgsc]

Thanks so much for your advice. My take-away from all this is that to get a matte finish (without a sandblaster) the alternatives are etching cream or sanding ( and maybe using the face-down side of fused glass as the top side). I guess I'll do some practicing with etching and sanding. Thanks again.

[charlie]

find someone who has a blaster? a six pack on friday afternoon around 5pm at a car body shop (who will have one) will probably work wonders.

[Morganica]

Or what Charlie said...a few nice words and a sixpack can work wonders. If there's a bit of a glass community in your area you can make friends with, you might be surprised at what turns up, too...

[Lynn Perry]

I seem to remember people posting about the difficulty of achieving a uniform matte finish using the standard off-shelf chemicals. I think the problem was the application of the product led to streaking.

[Morganica]

I seem to remember people posting about the difficulty of achieving a uniform matte finish using the standard off-shelf chemicals. I think the problem was the application of the product led to streaking.

Sometimes it does seem like just about anything--a slightly different dilution, different pressure in the application stroke, oils on the glass, residue from a price sticker, etc.--can affect how the etching cream does its job. I think most people, though, have problems because they either try to dilute the cream too much or they don't leave it on long enough. If you follow the directions exactly, measure carefully, and are scrupulous in the way you clean the glass (and your tools), it usually works pretty well.

But yeah, if sandblasting isn't possible I much prefer hand-sanding because I can completely control it.

[peter cummings]

I'll agree to all the above. Love a satin finish. Having used the etch cream and the sugar acid dip, I never want to go there again.
I found with the cream, when I took the first wipe OK, but taking a second wipe the line where the two met or overlapped, stood out clearly. Happened in the dip also, and it was impossible to correct.
I'd follow cybthia's tips.
Be careful with the local mechanic, there could be grease if she uses the blaster to clean parts like brake drums.