Shaping using grinder leaves marks

[Jeannette]

Sorry if this is covered already and there is a post or posts lurking that in cant find....

I've been grinding peices into some more precise shapes for use with a soft fuse. I'm left with what I suppose are grinding marks in the edges as the piece rounds off in the kiln. I can't see a way to avoid the grinding with some of the shapes that I need, so I'm wondering if I should be doing something to the glass before the fuse.

Appreciate your advice!
Jeannette

[Laurie Spray]

Be sure to finish all of your grinding with a fine bit.....not rough. Also scrub it
well before fusing. Never let it dry between grinding and cleaning.

[Jeannette]

Thanks, will try.

[Valerie Adams]

Work with a bucket or bowl of water next to your grinder; drop pieces in as soon as you're finished grinding to keep them from drying out. I scrub with a Scotchbrite pad under running water. Don't fire these pieces on Thinfire; the edges will fog up.

[Laurie Spray]

Valerie....I always hear that....but I fire on thin fire......no problems here! ???

[Valerie Adams]

Valerie....I always hear that....but I fire on thin fire......no problems here! ???

I suspect it's worse if the ground edges are on jewelry or components that are fired directly on the TF. If they're used on top of another piece, it's not a problem.

I gave up TF long ago (after it was causing MAJOR fogging problems with Tekta) and keep any ground edges wet, then scrub well, so I don't have edge problems. But I've seen enough of them to know that TF has been the major culprit.

[Drewcilla]

I had this problem with pendant sized pieces in the beginning. Advice about dropping the pieces immediately into water, following initial grinding with a finer grinding bit (I use 600), and scrubbing them well cured my problem immediately. I, too, use Bullseye Thinfire and don't have the hazing problem.

[JestersBaubles]

Valerie....I always hear that....but I fire on thin fire......no problems here! ???

Same here.

I've recently switched to Papyrus because of the easier clean-up, but I have never had a devit problem because of shelf paper.

Dana W.

[Jeannette]

Many thanks - I'll grind some pieces today and throw them in on a soft fuse to see what happens.
I'm not sure about not using thinfire, if I fire on kiln washed shelves I have to repaint them each time I fire...the scraping and waiting to dry is too time consuming to keep doing that every day. So I'll keep the TF in place for this shot and see what happens.
Thanks for this - it's a simple tip, really and never knew!

[Morganica]

I have had devit issues with fiber paper, not just thinfire. I suspect that it's most noticeable with thinfire because it covers such a large area of the kiln, and it's used so often. But if you fire on a blanket of 1/8inch fiber paper--at least with the fiber I've used--it looks the same.

I didn't think I had any issues, either, until I was doing a set of dishes and ran out of thinfire halfway through. As a result I fired about half the pieces with just kilnwash on the shelf, half with thinfire added. When I put them all on the table, I could tell exactly which ones had been fired with fiber and which hadn't: The fiber-fired glass wasn't as glossy as the kilnwash-alone glass, and looked as if it just needed a bit of cleaning.

At that point I realized that I was simply used to glass with a slightly duller appearance. It's pretty subtle unless you're just blowing out all the other factors in devit, so I think a lot of people simply don't notice it. And since I rarely use a piece straight out of a fuse/cast firing without coldworking, it's not something that bothers me much.

I've changed my processes, though--I don't use fiber on a final firing such as a slump or firepolish, and when I do use it I vent the kiln to at least 900F to allow fiber outgasses to escape. After a major casting stint, I junk-fire at least once to burn off as much residual contamination as possible. (I call junk-firing the process of firing non-critical stuff, or stuff that will be completely coldworked, at higher-than-normal temps, without any refractory in the kiln except the shelf, kilnwash and shelf posts, and with the vent open until the cooling cycle starts.)

I honestly don't know if the junk-firing helps much. I do know that pieces from the subsequent firings seem cleaner after I do it.

[JestersBaubles]

All that being said, if I understand correctly, the problem is with grinder marks, not devit. As was mentioned, if it's scratches from the grinder, you need to grind with a finer grit and then, for best results, work the edges with a diamond handpad (if your grinder isn't 400 or finer grit).

Dana W.

[Jeannette]

Sadly it didn't work keeping it wet and scrubbing (I was just hopeful), so I shall need to invest in a finer bit for the grinder. I don't find it easy to get supplies in the UK, so it appears this is the one finer than "standard" fitted to my grinder from new.
http://www.warm-glass.co.uk/fine-220-gr ... -2268.html
Is this sufficiently fine?

Thanks in advance.
Jeannette

[Valerie Adams]

Sadly it didn't work keeping it wet and scrubbing (I was just hopeful), so I shall need to invest in a finer bit for the grinder.

Did you try it without the fiber paper?

[Barry Kaiser]

I agree wholeheartedly with Dana.
The problem is that the edge is not ground well enough. We grind at 600 grit on the last pass. Works like a charm! We do wash thoroughly before the firing.
We also swipe it with a Boron devit agent (dirt cheap).

Barry

[Brad Walker]

Sadly it didn't work keeping it wet and scrubbing (I was just hopeful), so I shall need to invest in a finer bit for the grinder. I don't find it easy to get supplies in the UK, so it appears this is the one finer than "standard" fitted to my grinder from new.
http://www.warm-glass.co.uk/fine-220-gr ... -2268.html
Is this sufficiently fine?

No, not really. You need a 600 grit head, or something similar to that. Some people call it Ultra Fine.

Aanraku makes them in a two pack. Warm Glass UK does carry some items by Aanraku, but not that particular one. (You might ask them to start carrying it!)

I googled "600 grit grinder head United Kingdom" and found several on ebay.co.uk. They're mostly US companies selling them, but even with shipping I think the price would be competitive to the one you found on WG-UK.

And I would agree with others in this thread who posted a similar solution: always grind twice, do the main grinding with a standard head and then one pass with the ultra fine head. That solves the roughness and the devit issues. (We have two grinders set up for this purpose because it's faster than changing heads.)

[Morganica]

What do the grinder marks look like? Are we talking gouges, sandy-looking spots, big scratches, or what?

If you can't find a 600-grit grinding head, buy some 400- and 600-grit wet-dry sandpaper and a stiff sponge. Wrap the sandpaper around the sponge, dip it in water, and grind away. Won't take that long and is very controllable. Do the 400 first, until the marks are gone, then the 600. If the marks are really bad, start with 220 sandpaper.

Nice thing about the hand-sanding is you can apply it to more than the edge, if necessary..

[Mary Lou]

For pendants and small pieces, I only use an old grinding heads that have pretty much been worn down. Takes a little more time as it doesn't cut as quickly but it also doesn't leave the marks. As well as keeping it wet and like Valerie, I scrub with a scotch pad and soap under hot running water. Dry with clean towel and use gloves to finish the work.

[Drewcilla]

I agree that you can get them from US delivered to you for less. I get two 600 grit bits (Two-fers) for $25 here:

http://www.thegrindershop.com/products/bits

Email them to see what it would cost you to have them shipped.

[Jeannette]

What do the grinder marks look like? Are we talking gouges, sandy-looking spots, big scratches, or what?

Hmm, how to explain - it's perfectly smooth as you would expect on a full fuse, but on clear glass is appears hazy under the surface where you have ground to shape.
Because in the fuse the edges smooth and flatten out it spoils the appearance because it's like a tide mark on the areas that were ground.

Thanks for the links to finer heads, I'll have a look, it's just the taxes when it lands that are a problem! Sometimes double...depends on the weather

Appreciate your help!