jamesp
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Member since October 2012
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Post by jamesp on Jan 26, 2015 12:19:36 GMT -5
In a nutshell, there is small bruises and big bruises/spalls. Some can be seen with the eye. Many can not. It is only at the final stages that the small bruises can be seen. This is a huge problem w/obsidian. And real aggravating. And only in polish do those little spalls show. Very frustrating. It looks like I got a non-bruising process finally. Hoping to move forward captbob. A lot of great lapidary folks have major issues tumbling obsidian. It is tricky-period. And I will assure you that bruising is the reason. Laying down a fine polish is a start. That was a big victory. But it is superimposed on bruises. Same varieties of obsidian every time. Because some varieties spall easier than others. The forces that are required to break grit down seem to be very close to causing spalling. It is a fine line, I am convinced. This next run(ha,again), will be protected by sugar earlier in the 220 stage, instead of starting at the 500 stage. Hoping that the SiC 220 in sugar will take off the bruises and not add any in the process and then I can proceed forward with the next steps. Just to get a polish this time with short runs of added grit steps told me a lot. It is the best I have done so far. The Viking instructions are clear about this 'finding out at polish' poor results. And it is the reason many people throw in the rag on tumbling obsidian. There is no way of detecting the small bruises that make a polish impossible to achieve. Challenging to say the least.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,168
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Post by jamesp on Jan 26, 2015 12:36:16 GMT -5
It is a big advantage to have grit breakdown on most stones, not so convinced it is good for obsidian. Is this because damage may occur during this breakdown time? In that case, I would think that conditions within the tumbler need to change. Damage shouldn't happen simply because the rocks are allowed to run longer. They should get better with time - not worse! edit fer spellin'Yes, damage occurs as soon as you put the obsidian in the tumbler-IF the tumbler is beating the rocks too hard. During initial grind of one particular grit and after the grit has laid it's finish down, bruises can occur. IF, your tumbler is hitting your rocks too hard. The trick is to keep the rocks from hitting hard enough to get bruises. So definitely. The longer they stay in the tumbler the more bruises you get. Bruises on bruises.... From the minute you start the tumbler with the next step, they can bruise the first minute, right to the end of that step. and if it is 500/1000/5000/14000, you will never know till polish tells the truth, excepting large bruises that can be seen with the eye. If you can see bruises that big, your goose is cooked. That's for sure. Then you have deep fractures. And pieces will fall out throughout all steps at such bruises. So I am avoiding grit breakdown as much as possible. Just going gentle, and letting the abrasive do the work it was intended to do. Removing layers a bit at a time. Just like a cab machine does.
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Post by fantastic5 on Jan 26, 2015 12:56:08 GMT -5
After seeing the Viking in action on Saturday I can't imagine that you are getting spalling or bruising at the speed you are running. It is so much slower than my Lot-O. Could these be occuring during the cleanout?
I pulled some tears that I did in the Lot-O last year and they look great to the naked eye, but under loop magnification do have slight pitting. But I did polish them in a mixed batch with agate. I guess I am lucky they polished at all.
I also realized that I gave you some mis-information about my recipe. I use the AO 1000 for 12 hours, then clean and move to the polish barrel where I use the Rock Sheds AO Polish (not sure what the mesh size is). I think I told you that I reuse the AO 1000 in the polish barrel. I let that run for 48 hours followed by the addition of both Cerium and Tin oxides and I let that run another 24 hours. I wish I could remember who's recipe this is as I cannot take any credit for it. I found it here a few years ago when I was first learning.
Oh and completely off topic. I just love your dogs! When I went back to your house to change clothes I wondered about going into your house uninvited. The three girls just barely raised their heads when I walked in and simply look annoyed that I was interupting their naps. I'm so used to dogs that would not have allowed that. I was showing my husband Denise's website and hinting at the idea that I would love one of your dogs after our Eve passes away. But I think he really likes the bully breeds.
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Post by captbob on Jan 26, 2015 12:59:55 GMT -5
okay... I'm not yet to the finer grits and polish stages, so perhaps I have a large crow on my menu sometime in the future. I'll know in a month or so. Yes, damage occurs as soon as you put the obsidian in the tumbler-IF the tumbler is beating the rocks too hard. During initial grind of one particular grit and after the grit has laid it's finish down, bruises can occur. IF, your tumbler is hitting your rocks too hard. The trick is to keep the rocks from hitting hard enough to get bruises. So definitely. The longer they stay in the tumbler the more bruises you get. Bruises on bruises.... From the minute you start the tumbler with the next step, they can bruise the first minute, right to the end of that step. I will agree that the tumbler MUST NOT be "beating the rocks too hard". That's where my "In that case, I would think that conditions within the tumbler need to change." comes into play. Can't agree with: "The longer they stay in the tumbler the more bruises you get. Bruises on bruises...." IF conditions are right, MY thinking (which is rotary based) is that: longer = better. Just going on what my experiences have been to date. Obsidian is a new game for me as well. But, I've not (yet) seen these bruises. Time will tell in my case, so for now I will step back until I my load progresses to where I can make definitive comments.
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Post by captbob on Jan 26, 2015 13:03:57 GMT -5
uh... where is the party at James' thread? Where did ya'll go hounding / what did ya find? AND, did you make broseph82 carry all the rocks?
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Post by fantastic5 on Jan 26, 2015 13:19:09 GMT -5
uh... where is the party at James' thread? Where did ya'll go hounding / what did ya find? AND, did you make broseph82 carry all the rocks? forum.rocktumblinghobby.com/thread/69255/garnets-rutiles-new-pics-page?page=5#scrollTo=790393 check out page 5 for some pictures that Jimi posted. Careful captbob I can't let 'party' at James' get started. I just happened to be in Atlanta for a scholarship weekend with my daughter and managed to get away for a few hours to visit with James and his wife. My husband would frown on 'party at James' when I was supposed to be the dutiful mother at Oglethorpe University!
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jamesp
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Member since October 2012
Posts: 36,168
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Post by jamesp on Jan 26, 2015 13:33:49 GMT -5
Thank you fantastic5 for straightening captbob out. captain needs to go too. Bet he would keep all amused and some. captbob, broseph82 would NOT carry the rocks so I got him in a rear naked choke till he tapped out. After that, he was an angel. Us old guys have to keep the young bucks at bay. Actually the light walking made me stiff enough to roll off the bed this morning LOL
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,168
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Post by jamesp on Jan 27, 2015 15:17:43 GMT -5
Rerunning obsidian in vibe with sugar using SiC 220. After 24 hours it sure did breakdown. So maybe grit will breakdown in the next steps 500-1000 and 14,000 using sugar as a thickener. Like the batter, better than water, thicker slurry seems more protective. Will see.
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jamesp
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Member since October 2012
Posts: 36,168
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Post by jamesp on Jan 30, 2015 6:09:43 GMT -5
Sugar run #2 looking better after AO 1000. SiC 220 is breaking down well after 24 hours, ran it for 32 for safe keeping. 24 hours broke AO 500 well, best 500 finish ever. This is good. Will start polish Sunday(out of town Fri and Sat).
Recipe Rough in rotary 7/8 full with 50% hard filler till shaped 2 days SiC 220(prefer SiC 120/220) vibe assuming no bruises from rotary. (actual time 32 hours) If bruised, run SiC 220 for 24 hours several times till bruises are gone. Then do 2 days SiC 220 for final 220 finish. 1 day AO 500 vibe (actual time 16 hours) 1 day AO 1000 vibe (actual time 20 hours) 1 day AO 14,000 vibe ( not run yet, may have to run longer depending on how well AO 1000 broke down.
All AO from Rock shed. One tablespoon sugar per pound in vibe.
So, instead of doing 500,1000,5000 and 14,000 in 28 hours, doing 500, 1000, and 14,000 in 72 hours to overlap grit breakdown better.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,168
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Post by jamesp on Jan 30, 2015 18:28:11 GMT -5
Seems that a better finish happens with any grade grit when the slurry is thick like pancake syrup. That's thick. Both the 220 and the 500 ended up like pancake syrup, had intentionally left the top off to allow evaporation. It is thick enough to slow the action in half(or more) from when the slurry is straight water. The 500 was the thickest slurry ever, and it was getting the best reflection ever for 500 on obsidian. It was better than the 1000 reflection, and the 1000 was a good bit wetter and ran longer.
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