4cornersrocks
off to a rocking start
Member since August 2008
Posts: 21 
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Post by 4cornersrocks on Aug 29, 2008 12:33:01 GMT -5
My friend who is a glassblower made some glass rectangles for me to cut up with my trim saw then tumble into rectangular beads. I need to drill them too. Should I drill after tumbling? I have a harbour freight rotary and vibratory tumblers to use, btw they were gifts, lol... Are there any quick or easy ways to tumble glass, like a two stage process? I have tone of experience with stones, just none with hard (pyrex/borosilicate) glass. Thanks! Any tips will help...
...Dude
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4cornersrocks
off to a rocking start
Member since August 2008
Posts: 21
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Post by 4cornersrocks on Sept 1, 2008 7:41:23 GMT -5
anybody...
Bueller...
........
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vigodits
starting to shine!
Member since September 2008
Posts: 28
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Post by vigodits on Sept 15, 2008 21:37:29 GMT -5
I'm kinda sorta in the same situation. I am in the process of tumbling Youghiogheny Opalescent glass. It is hard. Started with 60/90, 7 days, 120/220, 7 days, 500, 3 days all Silicon Carbide. Then I did 3 days with 1000 grit AO. Next I did 3 days Cerium Oxide polish, then 3 days AO polish. There is the rub I could not get more than a luster. So now I have it back in the Cerium Oxide. The edges are beginning to shine but the flats are still a luster. I checked it with a loupe and it looks sand blasted. Oh I have been using plastic pellets with each grind.
Such has been my experience. I feel as though trial and error is going to be the order of the day. I don't know if that helps any but maybe we can flush out some more opinions.
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Post by connrock on Sept 17, 2008 6:12:42 GMT -5
Glass can be a bummer to polish.It has so many different compositions and I find they all need a little different technique to get that "wet" look on them.
Oddly enough the best shine I ever got on glass was from some old broken bottles I found at a home building excavation!
Looking through a jewelers loup is a great way to learn and solve some of the problems we have in tumbling.
That "sand blasted" look you see is the result of what the previous grit left on your glass.
The entire tumbling process is nothing but finer and finer "sand blasts" until we get to the finest "sand blast" which we call polished!
If you look at the shiny edges of your glass through the loup you will see that the "sand blast" is MUCH finer then the rougher parts.
This is a VERY good clue as to why the "flats" are not shining up for you.
In 2 words it's "surface contact" or actually the lack of it!
The reason the edges are getting polished is because they are having MUCH more surface contact with the other pieces in the tumbler.
The flats are just going along for the ride and don't have much surface contact.Why? Because there's nothing for them to have contact with.
If you take a copper penny and rub it on a rag on a flat surface with polish on it you will see that the edges shine up MUCH more then those areas that are not near the surface.The dull areas are not making enough surface contact with the polishing rag!!
Same thing with that glass in your tumbler.
How to solve the problem?
Marbles!!!
About 1/3rd or more of your load of marbles should solve that sand blast look for you.
If not marbles then small broken pieces of glass but that gets messy and sometimes leads to a lot of tiny cuts on your fingers and or hands.
Ceramic medium may be OK but I'm not sure if they may be too hard and will only cause you more probs by scratching the glass.
Optical grade cerium oxide works great in a rotary but it's expensive.You can use regular cerium oxide and let it run longer.
Hope this helps get that sand blast look out for you and explains why your getting it.
connrock
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vigodits
starting to shine!
Member since September 2008
Posts: 28
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Post by vigodits on Sept 18, 2008 8:46:37 GMT -5
Thanks much conrock. You confirmed my suspicions about surface contact but until you suggested marbles I was at a loss for solutions. So marbles are in the mix asap. Thanks again for the advice.
Lj
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stefan
Cave Dweller 
Member since January 2005
Posts: 14,113
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Post by stefan on Sept 19, 2008 9:03:51 GMT -5
borosilicate- being what it is- is a bugger to polish- no quick easy shortcuts- I would run the usual grits (60/90; 120/220; 500) then add a 1500 grit stage, a prepolish stage, and a final polish with either tin oxide, or aluminum oxide (I don't think cerium oxide is hard enough to polish boro)
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Post by LCARS on Sept 20, 2008 13:33:02 GMT -5
Cerium oxide should work if you give it enough time but tin oxide will put a shine on boro glass quicker.  (assuming you have suitably prepolished surfces) I can also add that for boro glass try running longer in the finer grit & prepolish stages with 25-30% less compound than usual and no recharging. I always have the best results with glass overall when I allow the grit to break down as much as possible before moving to the next stage. 500-1000 Al Ox grit followed by a coarse cerium oxide should have that boro glass gleaming after the final polish run... |
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lynskyn1970
noticing nice landscape pebbles
Member since August 2008
Posts: 93
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Post by lynskyn1970 on Sept 20, 2008 17:25:44 GMT -5
i don't have any experience in tumbling glass but i say drill them first before you tumble just in case you have some blow-out from the drilling. then you can just tumble out any rough parts. my 2 cents!!!!
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vigodits
starting to shine!
Member since September 2008
Posts: 28
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Post by vigodits on Sept 25, 2008 10:03:13 GMT -5
I think lcars post may have already answered my question. I am 6 days into the polish phase using 8 oz of Tin oxide in my 15lb Thumlers. I added to the original charge 2 tablespoon of borax. Marbles are the filler and grit carrier. The polishing slurry has become watery. Here are the results: This shot show the remaining matting  The next two are shot at an angle so some shine is visible.   It's almost there but not quite that wet look My question is (and I am noting lcars recommendation) should I add another tablespoon of SNO2? or should I just let it go another few days? I trust you guys. I have gotten further heeding your advice than I did trail and error on my own. Thanks |
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