deanf
starting to spend too much on rocks
Member since January 2007
Posts: 109
|
Post by deanf on Dec 7, 2008 19:04:21 GMT -5
I have had this happen in 2 batches recently and wondered if you have any suggestions ?
I have recently had 2 batches where the stones have been either cut from larger rocks to fit the rotary tumbler or where off cuts from slabbing. In both cases wherever there has been a flat surface the stones will be frosted (as if unpolished) while the edges will have a high luster. Not sure why the flats are not taking any sort of shine.
Any suggestions for me ?
Thanks !
Dean
|
|
rallyrocks
fully equipped rock polisher
Member since November 2005
Posts: 1,507
|
Post by rallyrocks on Dec 7, 2008 19:35:47 GMT -5
I usually have this problem if there are not enough smaller stones in the batch to carry the grit with some force against those flat areas.
Having enough little stuff seems to help minimize that issue.
|
|
Sabre52
Cave Dweller 
Me and my gal, Rosie
Member since August 2005
Posts: 20,496
|
Post by Sabre52 on Dec 7, 2008 20:07:02 GMT -5
Yep, if I'm running flat surfaced preforms, I put only a few in the barrel and lots of other sizes esp small filler stones. The flats grt polished very well because there's more surface to surface contact in the tumble....Mel
|
|
|
|
Post by bobby1 on Dec 8, 2008 0:12:08 GMT -5
Often when you polish slabs, two of them will get stuck together and remain that way until you open the tumbler and pull them apart. This will leave an unpolished circle on both of the stuck together slides.
Bob
|
|
|
|
Post by LCARS on Dec 9, 2008 2:18:36 GMT -5
I have seen this before, like the first few times I tried to put agate slabets or other flat faced materials in with a mixed batch. That was before I learned the tricks and secrets to getting killer results.  My gut reaction and short answer to your question is to say "run your stages longer with slabs in them and be very meticulous about cleaning and avoiding any grit contamination in between the stages". The effectiveness of abrasion over time is lowest in the center of flat surfaces and highest at sharp edges (why the pointy ends of stones wear down faster than round sides and dimples take forever to smooth out). One of many great things about tumbling though is you can always take the failures or ones you're just not happy with and run them again at the beginning of the apropriate stage in your next batch to fix them.  If it is just a crappy shine and they're not all banged up then start them again in a fresh prepolish stage on your next batch but run it longer to allow enough time for the flats to really get smoothed out. If they are banged up then it's back to the grind with a cushioned load and more patience. With slabs, I let stages run at least 25-30% longer than I would with just tumbled stones. I've been running my own mix of 500/1000 grit AO since I came by some for free and I usually let this run without any recharging of grit for at LEAST 8-10 days if i'm in a hurry to get them done, 12-14 otherwise. I do this to make sure all of the larger AO grit has a chance to do it's work and break down to at least the 1000 grit size before I go to my first polish stage. I am usually rewarded by semiglossy flats on my agate slabbies by the time they come out of prepolish and a liquid mirror shine after the final polish stage.  When I polish slabs in my 3lb rotary drums I always mix just a few in with a batch of various sized material. Too many slabs in a batch will likely start causing you problems. You have to use a good variety and quantity of medium to small and pebble sized stones and trimmings if available as filler material to get even grinding action and prevent them sticking together or to the sides of the barrel frequently. I hope you get the reults you're hoping for on your next attempt!  |
|
morticiamonroe
starting to spend too much on rocks
Member since October 2008
Posts: 147
|
Post by morticiamonroe on Dec 9, 2008 9:36:28 GMT -5
Great information from everyone here. Thanks! I need it, too!
|
|
|
|
Post by johnjsgems on Dec 9, 2008 10:02:39 GMT -5
If you don't have "a good variety of medium to small and pebble sized stones and trimmings" you can use non-abrasive ceramic media. In a "normal" batch fill the drum with rock to 2/3 full then add ceramic media to the 3/4 full level. The more flat pieces in the mix the more ceramic you will need to use. It also works as a filler in loads that are too small.
|
|
ejs
spending too much on rocks
Member since July 2008
Posts: 478
|
Post by ejs on Dec 9, 2008 12:35:47 GMT -5
I, too, like to use the ceramic media as "filler" to help increase abrasion in the coarse (60/90 SC) and medium (120/200 SC) stages. After that (prepolish 500 SC, prepolish 1000 AO, polish AO), I use a decent quantity of plastic pellets to help distribute the polish and cushion the load. Give that a try and let us know how it works out!
|
|
fanatic
starting to spend too much on rocks
Member since October 2007
Posts: 233
|
Post by fanatic on Dec 9, 2008 16:06:14 GMT -5
My experience is similar to LCARS. I tumble a lot of preformed pendants made from slabs all the way up to the standard 52mm x 38mm ovals. I had trouble at first with the flats not being nearly as shinny as I wanted. I started tossing in a lot of smaller material - mostly quartz and amethyst that I smashed with a motar and pestal. I leave them as small chunks - don't smash them to dust. I screen them and only tumble what won't go through a 4 mesh screen. I only use a filler in the polish stage and then I only use plastic pellets. I leave them in for a minimum of 14 days and I always use a burnish stage afterwards. Doing this I can put 8 of those 52 x 38 in mixed with smaller pendants in my 3 lb tumblers and I've had great results. The smashed small stuff I tossed in gets saved until I can find pairs to make into earrings. I've used them to make belly button rings as well.
|
|
