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Post by Rockindad on Feb 20, 2022 17:18:52 GMT -5
A few months back I ran a contest comparing a couple of different methods for tumbling Mahogany Obsidian, the link for anyone interested in the full write up: forum.rocktumblinghobby.com/thread/97004/spot-obsidian-contest-waysLong story short: 1) All Obsidian rotary tumbled to shape, 2) Split into two batches to be run in Lot-O using two different methods, 3) Document individual stones after they are run in their respective method, 4) Run contest to see who could spot differences between the two batches. Now the follow-up. In one of the posts in that thread I speculated that I thought any differences in the batches would be erased after a run in polish. We have since run the two batches in a proper polish run and it has been confirmed. Here are a couple of group pictures, I know individual shots would have produced much better quality but I am tired of putzing with this Obsidian now. After not seeing any difference with the naked eye we broke out an extra shop light and a loupe, still no difference. Now, we have already streamlined our means of tumbling anyway but if there was ever any doubt before there is none now. Not going to expend extra effort, time, money etc. to get the same results. Finally, if I thought the finished product suffered at all using fewer steps I would not hesitate in abandoning it.   For the record, with the exception of some softer porous stuff, the material used does not matter. We have done this with manmade glass, agates, jaspers, multiple obsidians, quartzes, etc. |
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Post by jasoninsd on Feb 20, 2022 19:24:28 GMT -5
Al, you and AJ really have helped a lot of tumblers with your advice and time consuming experimentation! Well...if you haven't helped "some", it's their own fault for not paying attention! LOL - Thank you guys SO much for everything you've been willing to contribute! Your results should be award-winning! (Wait...I guess they are!  ) |
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jamesp
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Member since October 2012
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Post by jamesp on Feb 21, 2022 6:37:58 GMT -5
Good to know that you have proven that steps can be cut to get the same results.
Alternate methods have apparently not been tried.
For instance - why the use of coarser aluminum oxide abrasives in finishing steps were not introduced 60 years ago into tumbling recipes is in itself a mystery.
This was a big oversight.
I am also of the opinion that most vibes were tuned for the most part for Mohs 7 rocks.
The Lot-O came along and verified this. And some UV's will do a high polish on obsidian and glass as well.
There is a point of operational functionality where a machine(like a vibe)can be designed to get the job done with excellent results with a very slight chance of failure. Call it a user friendly machine. Like a vibe that is set up to easily polish with a poor slurry for instance. Excepting the Lot-O, most of our vibes were designed years ago and most of them damage softer materials. Just saying the target for design was harder rocks. And that makes sense. A plethora of agates woods jaspers are available to make killer tumbles easily. Why not.
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Post by Rockindad on Feb 21, 2022 6:48:24 GMT -5
Al, you and AJ really have helped a lot of tumblers with your advice and time consuming experimentation! Well...if you haven't helped "some", it's their own fault for not paying attention! LOL - Thank you guys SO much for everything you've been willing to contribute! Your results should be award-winning! (Wait...I guess they are!  ) Thanks Jason, that's really nice of you to say. Honestly though the only reason we did it this way was because I was not aware of an existing thread that had a side by side comparison using the same material. The concept has been discussed multiple times in the past. jamesp has been a proponent for quite some time now as well as others. I believe the first time I read anything regarding the concept of minimizing steps was a post by Rich parfive where he was talking about skipping the 120/220SiC stage during rotary tumbling. Made a lot of sense to me. I'd bet that post is 12-15 years old by now. Interesting that this concept does not seem to have gained a lot of traction as it works even better on the agates/jaspers most seem to favor. |
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jamesp
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Member since October 2012
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Post by jamesp on Feb 21, 2022 8:05:25 GMT -5
Another point is that abrasives change grit size with time in a tumbler.
It doesn't work that way on a cab machine where it is efficient to use all steps since each grit stays the same size.
It does not take long for SiC 60 to breakdown to SiC 220 or even 500 inviting a skipped step.
Just leave the SiC 60(or even SiC 30) rolling long enough for the breakdown to occur.
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rocket
spending too much on rocks
Quality slabs for quality cabs in 2022
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Post by rocket on Feb 21, 2022 8:34:40 GMT -5
Thanks for all this detailed work. Could you summarize a 100% rotary conclusion..if there is one
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waterboysh
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Post by waterboysh on Feb 21, 2022 11:37:04 GMT -5
Hey Rockindad, I have a question for you about your obsidian. I'm actually getting ready to tumble some Mahogany Obsidian myself. Just waiting for the last of my Tiger's Eye to finish and free up a barrel. I've never tumbled anything softer than agate/jasper. Any tips for stage 1 in a 3 lb barrel? How long did you run them in coarse? Also... I have some Apache Tears. Depending on where I look, I see quite a few people saying to skip the coarse step and just start them in medium grit. I threw some of them into the Lot-o with a bunch of quartz pea gravel in 120/220 and after a full day, they've barely rounded off at all. I'm thinking this could eventually work, but might take a lot of time. Maybe I should do the 120/220 in a rotary instead? Not really sure, so looking for some tips here as well. Would just like to finish by saying your obsidian looks amazing and it makes me really excited to tumble mine. |
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Post by Rockindad on Feb 21, 2022 18:04:23 GMT -5
Hey Rockindad , I have a question for you about your obsidian. I'm actually getting ready to tumble some Mahogany Obsidian myself. Just waiting for the last of my Tiger's Eye to finish and free up a barrel. I've never tumbled anything softer than agate/jasper. Any tips for stage 1 in a 3 lb barrel? How long did you run them in coarse? Also... I have some Apache Tears. Depending on where I look, I see quite a few people saying to skip the coarse step and just start them in medium grit. I threw some of them into the Lot-o with a bunch of quartz pea gravel in 120/220 and after a full day, they've barely rounded off at all. I'm thinking this could eventually work, but might take a lot of time. Maybe I should do the 120/220 in a rotary instead? Not really sure, so looking for some tips here as well. Would just like to finish by saying your obsidian looks amazing and it makes me really excited to tumble mine.
We started out with 2 and 3lb. barrels so will confidently say no special considerations are needed. I like to have some hard material in the barrel to help break down the grit- ceramics, gravel, small agates, etc. This is really what the above discussions are about- understanding that your grit is becoming finer as the process moves along and using that to your advantage. Like most tumbles the rocks run in as many times in coarse as needed to achieve the desired shape/condition, this typically happens a lot faster with Obsidian than the harder stuff. Also... I have some Apache Tears. Depending on where I look, I see quite a few people saying to skip the coarse step and just start them in medium grit.....
For the results we are after I completely disagree with this. We are in the middle of running a few batches of Apache tears now and they get roughed in the rotary barrels with coarse SiC. Rotary is far superior for this work. We happen to be using 60/90SiC as we still had some left over from when we stocked more grits but wouldn't hesitate in using a coarser grade. Thank you for the compliment and I look forward to seeing yours as well. I think we had a little advantage when we started doing Obsidian as we kind of started in the hobby backwards as we did a lot of softer stuff early on. Obsidian almost seemed easy compared to materials that were porous/grainy, of mixed hardness, etc. |
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waterboysh
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Post by waterboysh on Feb 22, 2022 12:51:28 GMT -5
Well, as you said, after 2 days in 120/220 on the Lot-o, the Apache Tears are noticeably smoother, but not any more rounded than they started.  So I think once the Tiger's Eye finishes sometime in the next few weeks (hopefully... I feel like I've been saying "just a few more weeks" for over a month now) I'll throw them into the 3lb barrel for coarse using 60/90. Did you use the normal amount of grit and check them after 1 week or did you use less grit and check them more frequently? Just since I've never done anything this soft before, I'm leaning towards using half the grit and doing a wash out every 3 - 4 days. I keep my old slurry and add some back each week, so I won't have to worry about building up a new slurry every time. |
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Post by HankRocks on Feb 22, 2022 13:41:54 GMT -5
I don't expect those Apache Tears to get very rounded in a Lotto, it's just not going to grind away much very fast. Mine are run in a Rotary which is an issue if you do not have one. They only go to the Vibe(UV-18) for the Polish run. Here's a picture of a mixed run of Apache Tears, Ark Quartz and Tiger Eye, they all came out very well. A decent percentage of these did spend two runs thru Coarse.  IMG_1811 by Findrocks, on Flickr |
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waterboysh
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Post by waterboysh on Feb 22, 2022 14:57:03 GMT -5
Those are very nice looking rocks Hank. I do have a rotary. One 6 lb barrel and three 3 lb barrels. They just all have stuff in them at the moment.
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Post by Rockindad on Feb 22, 2022 17:37:28 GMT -5
Those are very nice looking rocks Hank. I do have a rotary. One 6 lb barrel and three 3 lb barrels. They just all have stuff in them at the moment.Ahhh....the old waiting game! Nice looking tumbles HankRocks, I gotta try the bottle caps sometime  . |
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