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Post by upsided0wnducks on Oct 23, 2013 19:05:45 GMT -5
Hi everyone, So I bought this beautiful slab of Feather Ridge Plume Agate, I intend to paint a pretty little winter scene on it but as I usually only buy cabs not slabs it didn't click that when the pictures said "wet" that meant it wasn't polished, I know, I'm silly. Anyway, it still has slabbing/saw marks and I'd like it at least to not have those if not a nice matte to semi-glossy polish to it so I can still paint on it and it looks nice you know? Here's the seller's pic, the slab is 5" x 4" x 6.2mm thick:  And my picture with an awful camera phone but it shows the marks I want to get rid of:  I have two other slabs I'm willing to trade and if that's not enough I'll pay a bit more as one of my friends told me polishing slabs takes the right tools and quite a bit of skill because they are flat. Here are the two slabs I have to trade: Ice Cream Opal Approximately 2.5" x 2" x 5.6mm thick:  Very Pretty Mystery Slab Approximately 4" x 3.5" x 5.6mm thick  If you're interested I intend to be painting on slabs and would like a person who would be interested in polishing slabs whenever I get the hair brained idea to buy unpolished ones that have amazing colors/scenes in them  Thank you in advanced! |
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Jon
starting to shine!
Member since June 2011
Posts: 41
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Post by Jon on Oct 30, 2013 21:57:37 GMT -5
How deep are those saw marks on your slab you want polished? And is the slab pretty flat otherwise across the face? I have a 16" dry slab polisher that I just got this last summer and have done over a dozen slabs on. Gives a nice mirror finish, but the general rule with slabs is flatter is better. With deep saw marks or any amount of curvature across the slab, the amount of time to polish can increase dramatically. A really nice flat slab can be polished in about a day and a half on my machine, but as soon as you get some deep marks or slight curvature to the slab, that time can go way up to a week plus depending on how bad the slab is.
When you run your had across the slab, do the saw marks feel like deep grooves, or are they just a little rougher than the rest of the slab? I may be willing to help you out assuming the saw marks aren't too horrible.
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Post by pghram on Oct 31, 2013 10:06:42 GMT -5
I've only done it a few times because it's labor intensive but you can do it yourself with some simple tools.
Have several pieces of thick plate glass (one for each grit, 60/90, 120/220, 500f) cut at your local hardware store. The glass provides a flat surface to grind on & keeps everything flat.
Mark the slab with a cross hatch figure (aluminum scribe or sharpie) so you can see when the whole surface has been ground.
Sprinkle the grit & a little water on the glass to form a slury. Start slow & add grit as needed. Move the slab, in a circular/figure-8 motion. Use the whole surface of the glass to keep everything flat. The grit will break down, just like in a tumbler.
Once you are satisfied, wash everything very carefully & go to the next grit & repeat. Spend some extra time on the 500f (you can use any fine grit that you have from 400-600) without adding new grit to allow it the break down to a very fine pre-polish.
I didn't have, or even know about, tripoly at the time, but it wouldn't hurt to add this step if you want to.
At the time I did this, I didn't have any eqpt. except a tumbler, so I bought a car buffing bonnet for my electric drill & used Tin Ox. You can achieve excellent results this way in a long afternoon.
Good luck & have fun.
Rich
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jollyrockhound
spending too much on rocks
Member since March 2013
Posts: 409
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Post by jollyrockhound on Oct 31, 2013 11:29:32 GMT -5
I use a Richardsons dry sander very fast:) Looks nice enjoy it.
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Post by snowdog on Oct 31, 2013 15:45:39 GMT -5
Sorry guys, you're way to late---- it's already at my house getting smoothed out ! Thanks for the advice tho. I'm using some diamond flat laps on it-- tried to do it on the machine but that outer rim is crumbly so am doing it by hand but using the diamond laps-- it's taking awhile because they are deep but it is getting there ----snowdog
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Jon
starting to shine!
Member since June 2011
Posts: 41
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Post by Jon on Oct 31, 2013 23:25:38 GMT -5
This is the way to do it:  180 grit 3m sanding screen from start to finish, doesn't sound like it should work, but it comes off with a beautiful mirror finish. I glue the slab to a block of wood, which attaches to bottom pulley, which rotates slab around while the sanding screen rotates around underneath the slab. A layer of dust accumulates on the disc which then serves as its own polishing compound. works great, just have to be careful with the dust as usual. |
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Post by sheltie on Nov 1, 2013 8:08:54 GMT -5
I use a wet polisher because there are no health problems involved with it and it finishes a slab with a high shine. The slab you have displayed will probably only have the shine you want in the one area where it isn't crumbly. You may want to have someone trim it down in size so the painting won't look "weird". I can't do dry polishing because of the inherent potential for health problems, but they do provide an excellent shine, as do the dry polishers. FWIW, we also have a Brent C Potters Wheel that we have converted for wettish polishing and it also works great.
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