Polishing 100 year old pieces of Slag Glass

Jewelry Discussion
1

Hello Everyone!!

I have a question about getting a glass like finish on 100 year old Slag Glass?
My finish sandpaper is 3,000 grit, I want to get a glass like finish on my finished product. Does anyone have a suggestion on what buff and polish type to use to get this type of high gloss finish.

Thanks

Lary1047

2

Hey Larry
I’m betting that you could use all the mechanical ways of polishing vitreous enamel pieces.

All the compounds- cerium and aluminum, and maybe wax at the end.

Curious what the glass will be and if the vibe of 100 yo glass will be preserved by all this fine polishing.

3

Aluminium Chloride I believe is what I was attempting to write. Not nearly enough sleep or coffee.

Let us know how it goes! Always interested in non traditional techniques and materials.

Cheers.
Janine

4

I think that they are oxides, at least they are in the lapidary world. I suspect that ceriunm oxide would work on glass. Depending on the shape of the object, you might be able to use small felt wheels, some of which you can buy already coated with various polishing compounds. I have never used them on glass, but try Zam and Fabuliuster. There are also diamond impregnated resin wheels and ways to use diamond grit in a carrier to polish. Since these are old objects, make sure that polishing them won’t take away from their value. This is often times the case for antiques…Rob

5

This would be a lapidary operation. Glass and stones are finished differently than metal. One important consideration is heat buildup; that’s why it’s usually a wet process. Excessive heat will cause glass (and other stones) to shatter; they’re sensitive to thermal shock. It’s also beneficial to rinse the fine dust away, both because it exposes the abrasive and for health reasons - you don’t want to breathe that stuff. If you’ve brought your glass to 3000 grit and it doesn’t have any scratches from coarser grits, the next stage is polishing. There are various abrasives used to give glass a final polish, but the most commonly used ones are diamond and cerium oxide. Diamond polishing compounds are usually dispersed in an oil base, while cerium oxide is made into a paste with water and used with a felt wheel, being careful to keep the surface moist to avoid overheating.

1 Like
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Thank you everyone!

Great answers, love the cerium oxide idea. I do use Fabuluster right now on small cotton buffing wheels. Gives a decent polish, but not the glass finish I am looking for. I do have cerium that I use for my Lake Superior agates so will try that.

Thanks to everyone.

Hopefully I can pay back through my knowledge and experimenting to help someone else.

Lary 1047

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I’ve had success finishing glass with a vibratory tumbler. I’ve used this technique for beach glass, shell, porcelain scraps. Depending on how rough the pieces are to start, use appropriate abrasive media in a vibratory tumbler. It will be a sequential process to get to a high shine. I’d finish with Diamond Pacific’s dry media “Vibra-Dri 25,000 grit” It is a magic media with diamond powder, garbanzo beans, and other stuff to add appropriate weight - safe for everything including opals.
Judy H

8

I think you meant aluminum oxide. The chloride absorbs water from air, is acidic and potentially neurotoxic. It corrodes metals including stainless steel. Aluminum oxide is corundum, Moh’s hardness 9. Only carborundum at hardness 9.2-9.5 and diamond at 10 is harder.

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Cerium oxide has a Moh’s hardness of 6-7… depending on what kind of slag you have, the hardness can be up to 7-7.5. Coal and steel slag are harder than copper slag. Glass has a range of hardness from 5.5 to 7. Cerium oxide matches glass and slag and will slowly polish it. Best use is for final finish. Diamond works faster. Use harder materials for shaping and roughing out…Your suggestion to keep the surface wet to avoid overheating is well taken. This applies to all lapidary work including diamond. Keeping the surface wet will also keep down fine silica dust.

1 Like
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HELLO EVERYONE!

Again thank you all for great suggestions and great back and forth discussions. Yes, the slag I am working with is from a 100+ year old iron foundries.

One question came up. Did I go into the wrong group. Someone mentioned “Lapidary” is there a special group that I should have to gone to for that area?

I do all my sanding and grinding in a enclosed tabletop tub using a water drip system yhst I designed and a flexible shaft to do all of my grinding and sanding.

Again, you all have been great with your suggestions and ideas.

Thanks

Lary1047