|
Post by Lazy Perfectionist on Apr 18, 2023 13:47:09 GMT -5
I've been on a steep learning curve to tumble obsidian, so I've been fixing "bruised" pieces from the tumbler by sanding out the chips on the flat lap. Afterwards I'm not sure which stage grit to tumble them with. I generally end up with an 800 diamond disk, but I realized that doesn't more scratches than a pre-polish tumble. So would tumbling in 500 grit pre-polish be enough to get out the sanding scratches or do I have to go back further? It seems like I'm constantly going back and forth between the flat lap and tumblers (rotary and vibratory), the flat lap to fix chips from the tumbler and the tumbler to fix scratches from the flat lap. ;-/
|
|
rocknewb101
fully equipped rock polisher
Member since October 2022
Posts: 1,368
|
Post by rocknewb101 on Apr 18, 2023 14:19:38 GMT -5
I'm by no means an expert, but I think if you sent the obsidian back to the 220 stage that would be sufficient to remove the flat lap scratches - maybe add in ceramic media if you haven't already - this will help to cushion. Obsidian is softer than your typical agate/jasper so I think the 220 grit would be ok. Obsidian is a tough one to get right IMO.
|
|
|
Post by manofglass on Apr 18, 2023 22:07:27 GMT -5
I don't get chips in the rotary I use pea gravel I use a 50 grit wheel to grind out the bad spots on obsidian then roll them in 35/70 grit tell the stones get smooth then they go to the vibe
|
|
|
Post by susand24224 on Apr 19, 2023 3:25:37 GMT -5
I didn't have any problem with obsidian either when I tumbled it but I added both a lot of ceramics (about 50%) and ivory soap shavings. I've been told, though, by others that tumbled it a lot that all obsidian is not created equal and some can be a real bear to get right. Maybe I was just lucky.
|
|
|
Post by jasoninsd on Apr 19, 2023 8:58:48 GMT -5
I've been on a steep learning curve to tumble obsidian, so I've been fixing "bruised" pieces from the tumbler by sanding out the chips on the flat lap. Afterwards I'm not sure which stage grit to tumble them with. I generally end up with an 800 diamond disk, but I realized that doesn't more scratches than a pre-polish tumble. So would tumbling in 500 grit pre-polish be enough to get out the sanding scratches or do I have to go back further? It seems like I'm constantly going back and forth between the flat lap and tumblers (rotary and vibratory), the flat lap to fix chips from the tumbler and the tumbler to fix scratches from the flat lap. ;-/ You didn't say how far you took the pieces on the flat lap. I've done what you're doing on my wheels...and I took the pieces up to the 600 wheel...that way I had to issues just moving to the 500 stage. If you're just using the 60 or 80 grit disk, then you'd definitely need to go to the 200 grit in the tumbler. I'm in agreement about LOTS of cushioning in the tumbler...
|
|
|
Post by Lazy Perfectionist on Apr 19, 2023 12:45:47 GMT -5
When removing problem spots, I take them up to 800 on the flat lap, so sounds like going into 500 grit should work.
I do use lots of cushioning (~75%), but still get a few tiny dings. Susand24224 made a good point about variability in obsidian. My pieces are highly variable, with lots of layers and sometimes ash pockets. I know those with ash pockets are definitely prone to chips and consequently scratching other pieces.
I'm still learning from my mistakes. so now I'm leaving out the heavy pieces, thickening the slurry to slow down the vibe, making sure that there are no chips/scratches before advancing, inspecting media for anything that might scratch, being more patient...
Fingers crossed for the batch in polish now!
|
|