mikeinsjc
spending too much on rocks
Member since June 2010
Posts: 329
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Post by mikeinsjc on Jun 20, 2010 17:25:56 GMT -5
Discovered this post while looking for ideas to make a grinder- very informative forum!
So here's my question: I am currently tumbling Lake Superior agates in a Lortone 3-12 lb. barrel tumbler. My technique, which works well on Montana Moss agates, is; 46/70 grit, 240 grit, 400 grit, cerium oxide, 10 days each cycle with plastic pellets on final polish. Barrels are half full, stones covered with water. After final polish, I end up with stones varying from highly polished to dull as a politicians biography. Is that the nature of these stones? Are the dullest stones destined for the flower bed or should I try retumbling all the dull ones together? Suggestions on improving my procedure are definitely appreciated!
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revco
starting to spend too much on rocks
Another Victim Of The Rockcycle
Member since February 2010
Posts: 162
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Post by revco on Jun 20, 2010 17:59:06 GMT -5
Welcome to the forums! It sounds like your process is working since you're at least able to get some polished rocks. Mixed loads can be tough, but I've found a couple things. Some rocks are particular about the polish that will coax a shine out of 'em. I generally try AO and CO and sometimes I'll get good polish from the AO, and others need CO. Some people have reported that tin oxide (TO) works well for those that have trouble with even AO and CO, but I haven't tried it. I keep my less than desirable results with the idea that I'll someday get some TO. Here's a list of someone's research into various polishes and types of rocks: www.utahrockhounds.com/tooelegem/tips/stonepolish.htmlThe other thing is that some types of rocks just won't take a polish. Some are too spongy/absorbent or the surface just isn't right for polishing. There's not a whole lot you can do there...it's a bummer sometimes when it's a really kewl rock, but that's the way it goes. Also, I generally let my polish go for two weeks+ because sometimes 7-10 days isn't enough. You might also try making sure you go to 2/3 with rocks AND pellets...1/2 full barrels don't tumble as well and you might not be getting good surface contact with your polish. Anyhow, hope that helps! |
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Post by susand24224 on Jun 20, 2010 18:41:56 GMT -5
Revco hit most of the highlights--I'll add a few more. Do you have mixed sizes in the barrel? It sounds like you have too much water--try adding water only to the bottom of the top layer of rocks. I agree that seven days is often not enough (especially if your size mix is not good and/or too much water). Since some are polishing, this could be a big part of it.
Also, I learned the hard way that not all AO is created equal. When I switched to a better grade of AO (slightly more expensive) I was able to avoid cerium oxide for even rocks that "traditionally" need cerium to polish well. If you have a lesser grade of AO, they will take longer to polish just because it takes awhile for it to break down to true "polish size." Or at least that's what I've been told.
To me it sounds like a possible combination of problems as the 1/2 full leaves a lot of space for sloshing about with too much water and lessens contact between the rocks. If the rocks are not a balanced load, this combination could take weeks to polish.
I hope at least one of these suggestions helps.
Susan
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Post by susand24224 on Jun 20, 2010 20:15:05 GMT -5
Oops! I just read your post again and saw that you are using a fixed "formula" for tumbling. Lake Superior agates are tough little buggers, and I suspect that with most of them, they are not ready for the next stage after ten days in 46/70 with no recharging. Bear in mind that your grit is breaking down the entire time so by the end of four or five days, it is not 46/70 and longer, except maybe a few particles here and there. I suggest that you take a close look at the ones that aren't polishing with a magnifying glass, loupe, or opti-visor in sunlight to see what kind of scratches, if any, remain.
Sorry I missed this the first time.
Susan
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mikeinsjc
spending too much on rocks
Member since June 2010
Posts: 329
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Post by mikeinsjc on Jun 20, 2010 21:07:55 GMT -5
I have never heard of recharging before. Under what conditions is it done? All steps? Also, is there a formula for how much grit I should be using, like tablespoons per pound of material? I use eight tablespoons on each step.
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revco
starting to spend too much on rocks
Another Victim Of The Rockcycle
Member since February 2010
Posts: 162
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Post by revco on Jun 21, 2010 9:54:48 GMT -5
For rough to get proper, it often takes anywhere from 3 to 10+ weeks and fresh grit needs to be added so it's effective. Recharging is the process, used primarily in the rough stage, where the stage is extended by adding additional grit. This happens typically in one of two ways - either by just adding new grit after 5 to 7 days or completely removing the rocks/grit and starting a fresh load. I do the latter as I classify all the rocks and pull those that are ready for 120/220 and add back in fresh rocks.
If I'm working with a totally fresh load, I'll often just throw grit in because I know it won't be ready after 2 weeks. The amount of grit is best determined by your load size. I generally use 1tbls per pound of rocks in course, which would be 12tbls in a 12lb barrel. You might get better/quicker results by upping your grit load...you'll also get a stronger slurry as well.
Hope that helps!
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mikeinsjc
spending too much on rocks
Member since June 2010
Posts: 329
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Post by mikeinsjc on Jun 21, 2010 18:08:09 GMT -5
On the Lake Superior agate lot that just came out of final polish, I noticed that although on many of the pieces I have a very acceptable shine on the flat surfaces, on the edges the finish is flat- by that I mean no sheen at all. Any ideas what might cause this uneven polishing?
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Post by susand24224 on Jun 21, 2010 20:08:34 GMT -5
Perhaps not enough small material to carry the polish properly, and perhaps the flat surfaces were smoother and more underlying scratches removed. I really can't imagine getting a good polish on Lakers after just ten days in coarse grind, though, unless they were pretty smooth to begin with.
Susan
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