ubermenehune
spending too much on rocks
Member since March 2016
Posts: 293
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Post by ubermenehune on Mar 27, 2017 12:40:23 GMT -5
I believe that the impact of grit contamination is overstated, if not a myth. Yes, this is contrary to one of the oldest and most widely shared axioms in all of tumbling. I realize my statement is akin to blasphemy, but hear me out.
- Grit breaks down in the tumbling process. Given. - Grit breaks down fairly aggressively. Within 2-3 days, SiC 60 (or any size for that matter) is pulverized into imperceptible dust; Maybe SiC 500 or smaller. Note that this is observed using a 15 lb barrel. I suspect the rate of reduction may vary depending on size and contents. Nevertheless, grit doesn't last very long.
Given those observations, I found it suspect that a few stowaway grains of grit could survive subsequent stages long enough to make any sort of meaningful impact. I tested my hypothesis in the following ways.
1. My first step was stopping meticulous cleaning between stages. I stopped looking for stray granules, repeated rinsings, and carefully scrubbing each stone with a toothbrush. There were no noticeable consequences after making this change. 2. I stopped using a dedicated barrel for the polish stage. Like most Lot-O users, I have multiple barrels. I've only been using one barrel for the past 2 months, and again, no noticeable impact. 3. For my past 5 or 6 standard tumble cycles, I stopped cleaning out between stages entirely (in the Lot-O). I will still rinse out mud/slurry between stages, but the rocks stay in the barrel. Once again, no difficulty achieving a wet shine.
I am by no means advocating that anyone follow my lead. Especially those new to the hobby who are still working towards achieving that desired shine. I've always been a maverick with little patience and certainly not someone to emulate. Just wanted to share some food for thought.
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Post by tims on Mar 27, 2017 13:53:28 GMT -5
Interesting. My biggest worry is usually the intact grit that accumulates around the rim of the lid on my QT12. Since I've been doing the 3-stage SiC80 / AO80 / polish I don't worry about thorough cleanout except after the last round of SiC and prior to polish, and for those it's usually necessary just to select what rocks look ok to move on regardless of contamination issues.
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metalsmith
Cave Dweller
Member since October 2012
Posts: 1,537
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Post by metalsmith on Mar 27, 2017 14:11:52 GMT -5
For tumbling, yeah, in general. But specifically, if you were in the polish zone and a coarse crumb of SiC spit out from under the hood, it would scratch things up. Mainly because the polish wouldn't break the crumb down quick enough.
For facetting, a definite 'no'; contamination can be a big problem.
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micellular
has rocks in the head
Rock fever is curable with more rocks.
Member since September 2015
Posts: 640
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Post by micellular on Mar 27, 2017 14:22:58 GMT -5
For facetting, a definite 'no'; contamination can be a big problem. Tell me about it.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Mar 27, 2017 15:33:59 GMT -5
I believe that the impact of grit contamination is overstated, if not a myth. Yes, this is contrary to one of the oldest and most widely shared axioms in all of tumbling. I realize my statement is akin to blasphemy, but hear me out. - Grit breaks down in the tumbling process. Given. - Grit breaks down fairly aggressively. Within 2-3 days, SiC 60 (or any size for that matter) is pulverized into imperceptible dust; Maybe SiC 500 or smaller. Note that this is observed using a 15 lb barrel. I suspect the rate of reduction may vary depending on size and contents. Nevertheless, grit doesn't last very long. Given those observations, I found it suspect that a few stowaway grains of grit could survive subsequent stages long enough to make any sort of meaningful impact. I tested my hypothesis in the following ways. 1. My first step was stopping meticulous cleaning between stages. I stopped looking for stray granules, repeated rinsings, and carefully scrubbing each stone with a toothbrush. There were no noticeable consequences after making this change. 2. I stopped using a dedicated barrel for the polish stage. Like most Lot-O users, I have multiple barrels. I've only been using one barrel for the past 2 months, and again, no noticeable impact. 3. For my past 5 or 6 standard tumble cycles, I stopped cleaning out between stages entirely (in the Lot-O). I will still rinse out mud/slurry between stages, but the rocks stay in the barrel. Once again, no difficulty achieving a wet shine. I am by no means advocating that anyone follow my lead. Especially those new to the hobby who are still working towards achieving that desired shine. I've always been a maverick with little patience and certainly not someone to emulate. Just wanted to share some food for thought. I do not clean out well uber. I agree with your theory 100%. I found a 3/4" ball of a 50 grit SiC grinding wheel in the last load I posted after final polish in the rotary. There must have been a 1/4 teaspoon of loose 50 grit SiC particles in the barrel. I looked for scratches. They were none existent. Stones very polished. It was this batch:
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Post by spiceman on Mar 27, 2017 21:23:35 GMT -5
I agree, but if you are using plastic media as a filler the coarse grit can embed in the plastic. It does not break down as good and if you don't replace the plastic filler the batch will have scratches. Maybe, only hard stones should be used as filler. Don't know.
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napoleonrags
Cave Dweller
Member since October 2015
Posts: 474
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Post by napoleonrags on Mar 27, 2017 21:40:03 GMT -5
Concure. I'm a lazy lapidary but do use a polish bowl in the Lot-o because I have one. Lot-Os are forgiving.
Gather no moss, Colin
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rollingstone
starting to spend too much on rocks
Member since July 2009
Posts: 236
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Post by rollingstone on Mar 27, 2017 22:09:08 GMT -5
I can't comment on the lot-o since I use a QT-6 Lortone only. I am fastidious about cleaning, and keep 3 barrels -- one for coarse grind, another for fine grit (120/220) and pre-polish (500F), and a third barrel for polish only. If I shine a light into my coarse barrel, I can see a myriad of glints from where silicon carbide grit has become embedded in the rubber. At some point those grit particles will escape back into the slurry. It might not matter much if they come loose in fine grind or even pre-polish, but I certainly wouldn't want them coming out during the polish stage, which is why I use separate barrels. It probably also depends on how blemish-free the rocks are that are being tumbled. If they are smooth and have no significant cracks or pits, then little cleaning is needed. But if they have pits that can trap grit that can be released in later stages, then they need a thorough cleaning (or outright rejection). Just to be safe, I do two washings between stages from fine grit onwards. No surprises that way.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Mar 28, 2017 3:27:42 GMT -5
I can't comment on the lot-o since I use a QT-6 Lortone only. I am fastidious about cleaning, and keep 3 barrels -- one for coarse grind, another for fine grit (120/220) and pre-polish (500F), and a third barrel for polish only. If I shine a light into my coarse barrel, I can see a myriad of glints from where silicon carbide grit has become embedded in the rubber. At some point those grit particles will escape back into the slurry. It might not matter much if they come loose in fine grind or even pre-polish, but I certainly wouldn't want them coming out during the polish stage, which is why I use separate barrels. It probably also depends on how blemish-free the rocks are that are being tumbled. If they are smooth and have no significant cracks or pits, then little cleaning is needed. But if they have pits that can trap grit that can be released in later stages, then they need a thorough cleaning (or outright rejection). Just to be safe, I do two washings between stages from fine grit onwards. No surprises that way. I have had a batch come out w/scratches too. On two occasions. Some of my barrels trap SiC 30 in a cavity and release it slowly over a long period. Worst case scenario when doing polish steps in those rotary barrels. Since switching to a vibe to do all finishing and the rotary to run SiC 30 that issue has disappeared. SiC 30 + rotary is kept a distance away from vibe. The vibe is a real fast abrasive crusher, large particles get crushed to nothing darn fast. Vibes are friendlier on this issue. Finishing in a rotary commands cleaning to avoid contamination.
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tkvancil
fully equipped rock polisher
Member since September 2011
Posts: 1,546
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Post by tkvancil on Mar 28, 2017 9:24:03 GMT -5
I agree if not a myth certainly overstated. From what I understand it is a very real concern when cabbing however. I have run my last three batches with multiple "flawed" rocks. All batches came out fine.
My rocks come out of stage one with only a rinse. No scrubbing. If one has a druzy pocket or some other void I'm keeping I'll give it a squirt with a spray bottle to get slurry out. Everything gets stored in water.
In the vibe I put in a little bit of liquid soap when the cycle is done. Let that run for a bit and then add enough water that the rocks look relatively slurry free as they come to the top. Rinse, squirt anything I see in voids as I reload next step. Fast and easy ... I hate cleaning anything.
I do have a dedicated polish bowl for the vibe even though I think cross contamination is overstated. Better safe than sorry I guess. My 220 thru pre-polish bowl does have some larger grit particles embedded in the plastic. Doesn't seem to bother anything though. Rocks always shiny out of pre-polish.
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jamesp
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Member since October 2012
Posts: 36,154
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Post by jamesp on Mar 28, 2017 16:19:10 GMT -5
Yes tk, better to be safe. CAN NOT hurt. I tumble rocks with lots of pockets carrying lots of grit. No doubt they pollute the batch. Rarely have had scratched rocks/dull rocks.
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ubermenehune
spending too much on rocks
Member since March 2016
Posts: 293
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Post by ubermenehune on Mar 28, 2017 17:37:06 GMT -5
Yep. Nothing wrong with "sterile" procedures. Better safe than sorry.
I choose to roll the dice, b/c I probably have less patience than most (according to my wife). Most of the time, tumbling is pretty forgiving, so if I screw something up, I can just toss it back in the barrel.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Apr 5, 2017 4:35:44 GMT -5
Yep. Nothing wrong with "sterile" procedures. Better safe than sorry. I choose to roll the dice, b/c I probably have less patience than most (according to my wife). Most of the time, tumbling is pretty forgiving, so if I screw something up, I can just toss it back in the barrel. The hard part is the coarse shaping. Rerunning a quick vibe run is nothing in terms of time and money.
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