How to polish a casted sculpture - WarmGlass.com

How to polish a casted sculpture

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la suisse
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How to polish a casted sculpture

Postby la suisse » Fri Oct 11, 2013 4:55 am

Dear all,

maybe I should put my question in the newcomer-part of the forum. I'm not quite shure about that.

A few month ago I did my first open mold castings and thanks to many postings I read I'm quite happy about the result. I continued to try around with open molds and find myself at a point that I need help.
Very silly question I think: How do I polish the surface of the sculptures?
I do have a Dremel... Would this be ok? Maybe I could find some equipment to polish with the Dremel after the grinding has been done?

I also bought some polish pads with a paste - but this doesn't work for these sculptures.

Thanks for your input

Joe Pfeifer
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Re: How to polish a casted sculpture

Postby Joe Pfeifer » Fri Oct 11, 2013 12:34 pm

Get a copy of the book: "The Joy of Coldworking" Everyone should have this book!
http://amzn.to/GJBXzT
If you watch you local classifieds for "lapidary equipment" you may be able to find some useful tools. There may be a local rock collector's club, which is also a great source.

Morganica
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Re: How to polish a casted sculpture

Postby Morganica » Fri Oct 11, 2013 8:09 pm

Joy of Coldworking is a very good book. Paul Tarlow's Coldworking without Machines is another good book, which discusses the use of hand-grinding/polishing materials. If you are going to do a lot of casting you should invest in both.

If your castings are mostly smooth, with little surface detail, it's relatively easy to use coldworking equipment to obtain a uniformly glossy surface. It just takes time and a little patience. However, the more detail on the surface, the more difficult the polishing becomes, because every detail must be polished separately.

Also, the top surface of an open-faced casting generally has a shinier, more glass-like finish than the surfaces against the mold. It can be difficult to get both surfaces to match unless you coldwork the entire piece. And once you coldwork a small part of the surface (for example, removing flashing resulting from a crack in the mold), you generally must coldwork the whole area. Otherwise, you'll always be able to tell the difference.

So it's always a good idea to review all surfaces of your casting before you start, and determine what level of finish you're trying to achieve. Then base your choice of coldworking methods on that finish.

Finely detailed surfaces can be very difficult and time-consuming to polish by hand. There are ways to automate the process, though. If the casting is small enough (usually the size of a large pendant or smaller), you can buy an inexpensive vibratory tumbler and take the casting all the way to a very high polish without losing significant surface detail. If it's larger, you can have the casting acid-polished, although that can be expensive and it can be difficult to find an acid-polishing facility.

Or you can fire-polish your casting. This means you clean and smooth the casting to about 400- or 600-grit level, then put it back in the kiln and run a firepolishing schedule. You will need to anneal for the full thickness of the casting, so it can be a long process.

A fire-polish can take the casting all the way to a full, glassy shine. However, it's very difficult not to lose some detail in the firing, and you must watch very carefully to make sure you don't actually melt the sculpture too far. And the surface that's on the kilnshelf, usually the flat back of the casting, will pick up that texture and lose its shine. That's not usually a problem because you can easily polish the flat surface, but you must be careful not to mar the rest of the casting when you do it. (and it's more work)

Personally, I prefer a softer, less glossy finish in my casting, so I usually finish my pieces with wet-dry sandpaper to about 800-grit, by hand. When I've firepolished sculptures I've usually been disappointed--the shiny surface looks too artificial, almost as if I've poured varnish on the whole piece.
Last edited by Morganica on Sat Oct 12, 2013 1:25 am, edited 1 time in total.
Cynthia Morgan
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Peter Angel
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Re: How to polish a casted sculpture

Postby Peter Angel » Sat Oct 12, 2013 12:01 am

An alternative is to lightly sandblast the glass surface and then paint/dip/airbrush a coat of clear acrylic.

This gives it a wet. shiny look.

You have to sandblast first otherwise the acrylic will easily chip off.
Peter Angel
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Lauri Levanto
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Re: How to polish a casted sculpture

Postby Lauri Levanto » Sat Oct 12, 2013 3:15 pm

Peter Angel wrote:An alternative is to lightly sandblast the glass surface and then paint/dip/airbrush a coat of clear acrylic.

This gives it a wet. shiny look.

You have to sandblast first otherwise the acrylic will easily chip off.


A good tip
that leaves one nagging question. Is it faking? I mean that a glass piece should
be of glass and not turn mattif cleaned with acetone or turn yellow in sunlight.

I have observed that some acrylic door pulls develop a mesh od tiny cracks
when exposed to sunlight and frost over years. That is not an effect I want in my glass pieces.
-lauri

Stephen Richard
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Re: How to polish a casted sculpture

Postby Stephen Richard » Sat Oct 12, 2013 3:58 pm

The question of permanentcy has be present in art for a long time. Some artists created work on unstable bases, giving museums great problems of conservation.
Steve Richard
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Peter Angel
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Re: How to polish a casted sculpture

Postby Peter Angel » Sat Oct 12, 2013 8:49 pm

Lauri Levanto wrote:
A good tip
that leaves one nagging question. Is it faking? I mean that a glass piece should
be of glass and not turn mattif cleaned with acetone or turn yellow in sunlight.



Lauri, I said it was a solution. I didn't say it was the best solution! :)
Peter Angel
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Tom Fuhrman
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Re: How to polish a casted sculpture

Postby Tom Fuhrman » Mon Oct 28, 2013 9:27 pm

there used to be a service in Tiffin. OH. that did acid polishing on customers pieces of glass. There are still some other sources outside of the US that does this type of work. It takes a very specialized set up to do this safely.

Morganica
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Re: How to polish a casted sculpture

Postby Morganica » Mon Oct 28, 2013 10:08 pm

Crystal Traditions of Tiffin, yep. I think they do it for their business and will accept baskets for artists' glass as they need it themselves. Can take awhile for them to have another batch to go through, and they tell you upfront that they're not responsible for anything that breaks. http://www.crystaltraditions.com/services.html

I think there would be a good market for a reliable, regular service in the US...but everyone I've asked about potentially putting in an acid polishing line has pretty much screamed when they saw the paperwork and insurance costs. I understand there is at least one other service in the US doing acid polishing, but I've never been able to find them. (PLEASE share if you know)
Cynthia Morgan
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peter cummings
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Re: How to polish a casted sculpture

Postby peter cummings » Sat Nov 16, 2013 7:17 pm

but everyone I've asked about potentially putting in an acid polishing line has pretty much screamed when they saw the paperwork and insurance costs

and I don't wonder Cynthia. I've done it, years ago, great finish, but the information about the acid and the people in trouble for using it really put me off. Before sand blasting a lot of cameo work was acid etched, and lots of workers died painfully and early.
While I'm not a fan of artificial finishes don't go there unless you have to, and can get someone in the industry to do it.
I'm working on a possible method but I've been learning painting etc for 2 years, so I'm back onto it.
Peter.

la suisse
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Re: How to polish a casted sculpture

Postby la suisse » Sun Nov 17, 2013 9:53 am

Thank you all for your input.
For the book "the joy of coldworking" I had it in my mind. Some month ago I ran over the pages and had the impression that it shwos the different items to coldwork but not really how to do it. Also I read of illnes of workers who did a lot of acid work, so I distanced myself of this method.

I have to think again for purchaising the book of Jonathon Schmuck; maybe I can take a second look at my reseller befor buying. I will certaintly buy the second book Cynthia mentioned. This sounds very interesting to me; never heard of this book. Thank you for this tipp!


Finally I finished my sculpture without polishing - however I'm quite happy with it; nevertheless open for your input.
The next one should be polished :wink:

Thank you all for sharing your experiences.
Attachments
le couple perdu.jpg
Last edited by la suisse on Sun Nov 17, 2013 10:09 am, edited 1 time in total.

la suisse
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Re: How to polish a casted sculpture

Postby la suisse » Sun Nov 17, 2013 9:58 am

Here is the second one....

The photos were taken on the occasion of a show in a very old storage building.
Attachments
l'homme.jpg

JestersBaubles
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Re: How to polish a casted sculpture

Postby JestersBaubles » Sun Nov 17, 2013 10:50 am

la suisse wrote:Thank you all for your input.
For the book "the joy of coldworking" I had it in my mind. Some month ago I ran over the pages and had the impression that it shwos the different items to coldwork but not really how to do it. Also I read of illnes of workers who did a lot of acid work, so I distanced myself of this method.


That is my impression of the book, too. I read it from cover to cover, and it tells you all the tools for coldworking and what you use them for, but not HOW to use them.

If I recall correctly, it was also full of typos, which, as an anal-retentive used-to-be tech writer, that kind of thing drives me crazy (and gives me less confidence in the material I am reading...).

2 cents,

Dana W.

GuyKass
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Re: How to polish a casted sculpture

Postby GuyKass » Sun Nov 17, 2013 12:42 pm

There is another options to HF, it is still fairly dangerous, and I have never personally seen the results so I can't swear to anything.

But disclaimers being said, it is called something like Sugar Acid etching,

I read about it in Henry Halem's book (which I would highly recommend to anyone doing anything in glass, as it gives an excellent background in a lot of areas.)

These are the ingredients:

1.5 litres of water
1kg Amonium bifloride
1kg sugar
12 grams barium sulphide

I don't know the mixing process etc.

I didn't really look into the Barium Sulphide, but the Amonium Biflouride seems to be what does the etching. By the same token when you read about it, it is fairly scary stuff unto itself. Evidently (at least is these parts) it is often used it at car washes to clean tires and wheels. But regardless, it's pretty strong stuff.

I can find Henry's book at the moment, but I will search it out, and if anyone wants me to get you all the info, I would be happy to.

Guy

peter cummings
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Re: How to polish a casted sculpture

Postby peter cummings » Sun Nov 17, 2013 5:07 pm

same warnings apply to the "sugar acid"
I rather like the spiritual look of the works as they are. nice sculptures that suit surrounds.
Peter.

FusedLightStudio
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Re: How to polish a casted sculpture

Postby FusedLightStudio » Wed Jun 27, 2018 4:43 pm

I’d like to hear more from Cynthia and anyone else about hand-polishing cast glass. In a casting workshop I just took, the only techniques demonstrated were: potter’s wheel with sanding surface; loose grit on plate glass; wet belt sander.

I don’t have the room or money for the potter’s wheel or wet belt sander, but the loose grit seemed soooo messy. And it would take up some space, too, if you used three or four grits.

I was thinking, why not use waterproof sandpaper sheets, and then you could sit comfortably and listen to music while polishing a piece by hand.

Any confirmation or details on the sandpaper technique?
Lisa Schnellinger
Atlanta, GA

Morganica
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Re: How to polish a casted sculpture

Postby Morganica » Wed Jun 27, 2018 5:04 pm

Hand polishing is massively satisfying, both to the practitioner and to the collector (or whoever is petting the glass after you're done). ;-) But it does take time and it's not for people who don't want to end up with arthritis in the hands or whatnot.

Paul Tarlow's coldworking book explains it very, very well and I'd urge you to grab a copy if you can. But it's a fairly simple and inexpensive process: Go to the hardware store, get a pack of wet-dry sandpaper in assorted grits (the dark charcoal-colored stuff, starting at about 120-grit and going up as high as you can find but at least to 600-800), and a couple of stiffish hand-sized scrubbing sponges. Then hit up the thrift store for a cheap rectangular metal baking pan, ideally an inch or two bigger on both sides than your biggest glass piece, and maybe 2-3 inches deep.

Now get a piece of old bath towel and/or an old piece of packing or electronics foam, cut to fit the bottom of the pan. Put one or both in the bottom of the pan, get a pitcher and fill it with warmish water, another bath towel you don't care much about, and set them all down in front of the TV on a table. Pull up a nice, comfy chair or sofa.

Sit in comfy chair/sofa, turn on a movie, and put pan with foam on lap. Pour in enough water that it peeks over the top of the foam/towel and splashes a tiny bit. Put the glass on the foam, get out the coarsest sandpaper and wrap a piece around a scrubbing sponge. Dip the paper-wrapped sponge down into the water until it's saturated, apply it to the glass...and start sanding. Don't kill yourself, just keep your strokes firm and even. The sponge behind the sandpaper helps push it into crevices and even out the abrasion. The extra towel is what you dry off your hands with when you change channels.

Every so often, get up and rinse off the glass, see how far you're getting. When the dried-off piece looks pretty evenly cloudy (or scratched up), wash it thoroughly, rinse out your pan, and move to the next smaller grit size. (I've found it's a good idea to keep a set of foam/sponge/toweling for each grit to avoid scratching up your nice piece, but a lot of the time just rinsing well is enough)

The texture of hand-finishing isn't like anything I've felt except for the finish you get from aluminum oxide in a sonic vibratory tumbler if you're really careful and stop before full polish. It's like silk, very sensual. I've gotten so I prefer it to a full polish. If you take it all the way to 1200-1600-grit it'll glow pretty well, but harder glasses/lower grits/your-hands-got-tired-so-you-stopped may need a light oiling to bring out full color.

Update: If you really get into this, 3M makes little square flexible diamond-plated sponges that are wonderful for speeding up the process. You can buy them separately or in a pack, from I think 80-grit up to 600 or something. The nice thing about them is that, as the diamonds wear out, the pad gets better and better at producing a softer finish, and when it finally does wear out completely, now you have a sponge that's superb for covering with wet-dry sandpaper and continuing. The diamonds are always going to be more aggressive than wet-dry sandpaper, so once you've done most of the work with diamonds, you switch over and finish with a high-grit wet-dry anyway...

3M also makes a rigid diamond pad that's much easier to find. The problem with rigid sanders, though, is that they tend to knock off the peaks and even out the surface, which is exactly what you do NOT want in a textured sculpture. A thin, flexible sponge will follow the contour of the piece.
Last edited by Morganica on Wed Jun 27, 2018 5:50 pm, edited 1 time in total.
Cynthia Morgan
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"I wrote, therefore I was." (me)

FusedLightStudio
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Re: How to polish a casted sculpture

Postby FusedLightStudio » Wed Jun 27, 2018 5:31 pm

Wow!!! Cynthia, I’m so grateful to you for this detailed description! It sounds like just what I want for the pieces I have. THANK YOU for taking the time to write it up!!!!

Update - thanks for that info about the 3M pads, too!!
Lisa Schnellinger
Atlanta, GA

Joyce Walters
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Re: How to polish a casted sculpture

Postby Joyce Walters » Fri Jun 29, 2018 3:32 pm

And it is also wonderful to have you writing about glass again!
You do it so well.
Joyce in MT


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