Minnesota Daniel
freely admits to licking rocks
A COUPLE LAKERS
Member since August 2011
Posts: 891
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Post by Minnesota Daniel on Dec 14, 2009 23:25:58 GMT -5
So how much grit are we supposed to use? For the SiC stage, rotary, I've seen instructions range from two or two and a half tablespoons per pound - The Edward E Smith, to half that much. In a "3 pound" Lortone barrel, how much does experience demonstrate is enough?
Logically, as the rock becomes ground, there will be less contact surface, so less grit would last just as long, except we add ceramic media to increase the contact area, and use the same amount of SiC for each stage. Right?
Dan
I'm a recovering analytic, it's a 22 stage program.
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Post by superioragates on Dec 15, 2009 0:05:57 GMT -5
Daniel, Love your signature...gotta love those brats! I have a 3 lb thumlers, and I use 3 tablespoons in the rough, but then I am grinding lakers, and they are hard as heck! Someone will let you know for sure what their methods are in the rotaries tho.!
Marie
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Post by johnjsgems on Dec 15, 2009 4:16:16 GMT -5
I think you will find a tablespoon per pound would do it. Load drum to 2/3 full, add ceramic to bring it to 3/4 full. Add grit and water to near top of load (rocks sticking out of water). I usually open the drum after 3-4 days (the old books all said to do this to "burp" gas build up) and check the slurry thickness. You can adjust water/grit if needed. If progress is slow or not a good slurry add a teaspoon or so. If too thick pour out a little and add water as needed.You can also try using whatever Lortone recommends and check it in 7-10 days. If all the grit is broken down recharge if needed. If you still have grit not broken down you had too much in there. The wonderful thing with tumbling is it really doesn't matter. Almost any way you do it it will work. It may take longer or shorter time but it pretty much will work. Blasphemous words, perhaps.
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Post by 150FromFundy on Dec 15, 2009 7:32:23 GMT -5
I use 3 heaped tablespoons per 3 lb barrel for the grit stages. I reuce to 2 heaped tablespoons for the pre-polish and polish.
I have tried inceasing the grit expecting to speed things up, but it just takes longer for the grit to break down, so there is no real time saving.
Most instructions are "heavy" on the grit requirment. I think they are in collusion with the SC and AO manufacturers.
Darryl.
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chassroc
Cave Dweller 
Rocks are abundant when you have rocktumblinghobby pals
Member since January 2005
Posts: 3,586
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Post by chassroc on Dec 15, 2009 13:31:17 GMT -5
As you would expect, there are personal answers to questions like "how much is just enough". I would ditto John's answer with these caveats:
1) Rotational speed affects the action
2) Excess water slows the action
3) Slurry increases the action
When you open the barrel, feel the rocks and slurry. If they feel "gritty" you probably used too much. Even that is open to question since the coarse grit will still be somewhat gritty when it breaks down to medium grit. So it's really a philosophical question.
Charlie
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montezuma
off to a rocking start
Member since December 2009
Posts: 21
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Post by montezuma on Dec 16, 2009 10:48:59 GMT -5
Okay, if you are not in a hurry, add extra water?
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Post by Toad on Dec 16, 2009 11:12:06 GMT -5
Too much water and a slurry might never form, or near enough. The only time I deliberately added too much water was when I knew I wouldn't be able to re-charge on my regular 7-day schedule. So I just added a bit more so that the slurry wouldn't become too thick.
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Minnesota Daniel
freely admits to licking rocks
A COUPLE LAKERS
Member since August 2011
Posts: 891
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Post by Minnesota Daniel on Dec 18, 2009 16:29:25 GMT -5
Great answers, thanks a lot. I have a question though. 500 grit, pre-polish or polish form suspensions -- that's a slurry. If I run Lakers with 60/90 grit, and check it later though, all I see are rock, water and grit. The grit is too heavy to become suspended in the water. So is there a magical way to make the coarser SiC form an actual slurry, or are we talking about what we imagine the contents of the barrel to be like when it's rotating?
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Post by deb193redux on Dec 18, 2009 16:31:24 GMT -5
no course does form a slurry. can tak a few days.
possibly lakers are already rounded a bit and darn hard to boot so the slurry takes even longer.
I would consider a thickener. unless there is too much water. more rounded stones tend to make for larger gaps between stones and that accomodates more water. but if you have the proper small filler it is unlikely too much water.
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Minnesota Daniel
freely admits to licking rocks
A COUPLE LAKERS
Member since August 2011
Posts: 891
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Post by Minnesota Daniel on Dec 18, 2009 16:49:07 GMT -5
Yes, I think Lakers are about 10.5 on the Mohs scale. Are there any thickeners that are not, will not become, growth media for bacteria or yeast?
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Post by johnjsgems on Dec 18, 2009 19:45:06 GMT -5
I don't know about thickeners but non-abrasive ceramic media or small rocks in the mix will speed things up. If you don't form slurry you may need less water. If the rocks are water worn already you may not need a long run in 60/90 anyway. Speaking of organics, do you have to wash the rocks well before you start like many beach rocks/river rocks?
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Minnesota Daniel
freely admits to licking rocks
A COUPLE LAKERS
Member since August 2011
Posts: 891
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Post by Minnesota Daniel on Dec 18, 2009 20:47:34 GMT -5
I use ceramic media almost always, especially the smallest size, so in that sense I am running a "mechanical" slurry of sorts I guess. I've run agates, jasper and quartz that were collected from gravel pits, so I have never had a problem with organics there. I did make the mistake once of following some written advice about using sugar to thicken the slurry. What was I thinking? The bucket I use to collect the used grit and polish became an alcohol producing mineral mash until it became infected with bacteria and stank like you wouldn't believe.
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Post by johnjsgems on Dec 19, 2009 10:43:21 GMT -5
Wow! Now that I know I can make alcohol I'll have to find time to tumble again!
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NorthShore-Rocks
fully equipped rock polisher
Member since December 2008
Posts: 1,004
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Post by NorthShore-Rocks on Dec 19, 2009 12:55:13 GMT -5
IMO The most important factor in a Laker tumble is the ratio of large, medium, and most importantly... the little stones. You need a lot of littles and their enormous surface contact for a successful batch. Yeah, you can substitute ceramic media for the little ones, but hard little Lakers are my work horses and I haven't found anything better yet. Plus, those little Lakers are a lot more handsome than the ceramic when shined up! Keeping that ratio intact as you go through weeks and weeks of rough grind is important too. As you pull rocks out and lose mass through tumbling, you need to replace the volume keeping the ratio in mind. When in doubt... add tinnies. I don't think I'd worry too much about thickeners in the rough stage. If you keep it too thick, you are in for one heck of a marathon tumble. Steve Edit: As other have said here... learn the feel of the rocks and slurry when you open and check your batch. There's no question when you need to go longer or it's time to recharge. If you're consistent on how much material, water, and grit you put in the barrel, you won't get many surprises and the whole process will become routine. For me, the amount of grit just determines how long I tumble that round. "Logically, as the rock becomes ground, there will be less contact surface..." I don't think this is true, but others may chime in. Although there is more surface area when the rocks are larger, as the bumps and cavities are ground to a more uniform surface, I believe there is more surface contact with the rocks, as they fit together better and the spaces between become smaller.  |
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Minnesota Daniel
freely admits to licking rocks
A COUPLE LAKERS
Member since August 2011
Posts: 891
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Post by Minnesota Daniel on Dec 19, 2009 17:39:33 GMT -5
I don't substitute ceramic for small rock if I have small rock. What I have in with the agates is small-sized scraps of chalcedony and pet wood, and a big handful of emeralds too. Also, in this last recharge, I added a handful of similarly tiny (1/4 inch to 1/2 inch) sapphires and rubies I had laying around. I just inspected it, and the Lakers are actually doing a pretty good job on them.
Unrelated question, sort of: Is the mustard on the outside of a Lake Superior Agate, limonite?
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Post by Jack ( Yorkshire) on Dec 21, 2009 1:20:41 GMT -5
Hi Dan
How much Grit?
I work on a 6 day cycle and if there is rough grit left over at the 6 day period there is to much grit,
You can check earlier to see if the grit is working and progressing to grind , but in my experiance in 6 days at 42RPM in a 6" barrell you will find the grit is spent and there is a good muddy goop there
Jack
Yorkshire UK
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chassroc
Cave Dweller
Rocks are abundant when you have rocktumblinghobby pals
Member since January 2005
Posts: 3,586
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Post by chassroc on Dec 21, 2009 9:21:43 GMT -5
Assuming that slurry is good, you jump start it by saving (some) slurry from prior coarse tumbles.
Charlie
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Post by Toad on Dec 21, 2009 12:02:08 GMT -5
Manufacturer recommendations have worked for me.
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Minnesota Daniel
freely admits to licking rocks
A COUPLE LAKERS
Member since August 2011
Posts: 891
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Post by Minnesota Daniel on Dec 21, 2009 19:05:26 GMT -5
Summary:
Probably 3 heaping tablespoons of of SiC per 3lb barrel is about right.
Be sure to have the correct amount of rock, and a good mixture of sizes, at the start and as you go along.
Fill the water to just under the last layer of rock.
After a week or so, feel the mix. If there is still a fair amount coarse grit, I probably started with too much. If it's all mud, check it sooner next time to see when it becomes mud. Re-assess the amount of grit to use. Recharge and tumble on.
And my own axiom: EVERYTHING is rare on eBay, and almost everyone is dumping their "old stock". In my head I substitute the words "silly old stock" - works for me! (but I still don't buy it)
The corollary axiom: Evaluate the cost of the grit vs how long it's going to take for the first stage, to make sure that by the time it's all done, it didn't cost more for the abrasives and polish than the quality of the rock merited.
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turnedstone
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Member since January 2006
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Post by turnedstone on Dec 22, 2009 1:04:25 GMT -5
Hi Daniel Looks like you got some good advice here from some very good tumblers.
chassroc said above:Assuming that slurry is good, you jump start it by saving (some) slurry from prior coarse tumbles.
Someone on here said this when I first started on here(May have been him can't recall who now). I decant all of my slurry after it settles out pour the water out let it dry out break off a chunk instant slurry. I have done this on every rough grind tumble since works great, use less on softer stones.
George
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