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Here is what I have found out. Slabs have a tendency to stick together in the 12 pound barrel tumblers. Because of this tendency, they have to be kept apart in the tumbling action.
To keep the slabs apart there must be a good quantity of small sized rocks added to each barrel of rocks as they are tumbled. These are from BB sized up to bean sized. Some people just throw these away if they crack up their own rock. I keep all of the floor sweepings - the stuff that is left over after I crush up my rocks. I throw all of these little pieces into the barrel with my other small broken rocks that I want to tumble.
If you did not keep the small pieces when you broke your agates into small pieces, get another chuck of agate that you do not plan on using and just break it all up into the bean sized pieces and use this in your next coarse grit load. Then keep these same pieces all the way through the process.
I did not get a good finish when using the plastic pellets as these are only recommended in the final two stages so I do not recommend using any kind of plastic pellets in the tumbling process. If you need a filler in the pre-polish or polish stages, use small blocks of hard wood or 2 inch lengths of a dowel stick.
For each load I can have as much as 1/2 load of slabs, 1/4 load is the largest sized rocks wanted and then 1/4 load is smaller rocks you want polished. When the barrel is filled to the (about � full) or the recommended amount, this is the time to add about 1 pound of the small bean and pea sized rocks. These just fit in between the rest of the rocks and act as that I call "scrubbers". The reason you can have more of these is they go in between the larger rocks and only take up air space instead of volume. They are actually the grinders as they carry the grit in between the slabs to grind off any saw marks and rough spots. They also grind in between the crevices and curves of the other broken rocks. They also carry the polishing powder so that these areas are polished. I like the way my slabs come out.
One reason people do not usually put the real small chips of rock in the tumbler is that the tumbler manufacturer does not tell them to do it. Another reason is they do not think they will have a need for them. Anyway who needs itsy bitsy tiny polished rocks? They might just be something that would be thrown away or discarded after the load was finished anyway. Since I set up and sell stuff at rock shows, what I do, though, is to put these real small rocks in plastic bags or boxes to sell to kids. Save them for club shows. Let them give them away. Any polished rock you cannot use, just give to a rock club. Just ask them if they can use them and most will gladly take all you can polish.
The other thing that I would mention to people is the time I let my loads run. I usually let my loads run 14 days. (I try to use every other Monday as my tumbler day. Set a two week schedule for doing tumblers so you do not worry about when it is ready.) For the rough grind, I find that for many of the rocks one time through is not enough time for them to look the way I like them. When I take my rocks out of the rough grind, after washing, I will spread them out to dry. All the rocks that are not as smooth as I want them to be go back into another rough grind.
When the rough grid load is really good these rocks then go into the second 220 grit stage of grinding. This is also for the 14 days. It never hurts them to go this long. (When you have not put too much grit in this stage, you can run it for 4 weeks thus skipping the pre polish stage. The grit has to have been used up and ground down very fine in order for this to work.)
The next stage is a pre polish. I am using an alumina for this. This again is for 14 days. This alumina will produce a kind of foam so it is easy to keep track of this step. The next step is the cerium oxide polish. 14 days is good for this also. I give the rocks an hour or two in a laundry soap wash (burnishing) to finish it off. The rocks are then dried and ready for sorting and separating. If there are some rocks (and there usually is only a few) that I don't really like the finish, I either throw them into a kids box or if I think they would be good if re- tumbled, I will put them in the next batch of rough.
My washing process for the coarse grit of a 12 pound barrel after 14 days is as follows. I work outside on a bench. I use plastic tubs that I can put a plastic strainer in. I dump the rocks into the strainer so most of the mud drains through. The top part of this mud is disposed of. The small rocks and any leftover grit in the bottom is saved for the next coarse grit load. You can tell what is grit by adding water to the bottom inch of sludge and again just dump off the top dirty water. The grit will be fine black looking grains. except any small rocks that go through the holes in the strainer.
Pictures to come.
I have a place beside my house that is out of the way and kids can not usually walk in it where I dispose of the waste sludge. You should find a place in the back yard, near the fence or behind a hedge for the tumbling sludge. I have seen an outside storm drain in the street used to dispose of the tumbling mud.
DO NOT PUT ANY OF THIS MATERIAL IN YOUR SINK DRAIN AS THE HEAVEY PARTS SETTLE AND TURN TO A SOLID MASS THAT WILL CLOG THE DRAIN.
I then wash the rocks using two or three small plastic tubs. The water gets cleaner by the second or third wash.
I save all the rocks but no coarse grit for the 220 stage. I use wire classifiers something like gold panning classifiers or strainers: � inch, 1/4 inch, 1/8 inch, and then screen wire size to separate the sand and extra coarse left over grit. (I made my own with metal mesh material.)
Pictures to come.
For the next stage � the 220 grit � I want all of the rocks except anything that goes through the screen wire size strainer. What goes through the screen wire may contain some coarse grit. All this rock material (sand) is saved for the next coarse grit. Remember: I need all the small rocks I can get to scrub between the slabs.
After the next 14 days are over I use a pre-polish and clean the barrel the same way.
When the pre- polish is done I do the same with the polish. (I use the cheaper cerium oxide for this.)
When the polish is done I clean the stones and then use a 2 hour laundry soap burnishing. (Rinse the soap off these rocks and they should still appear wet even when dry.)
MORE ABOUT MY TUMBLING FROM A LETTER WRITTEN TO A FELLOW LAPIDARY
On my web page about tumbling I did not say anything about the amount of grit I used as I assumed most people had the directions that came with their tumblers or had done research for that. Now I do not really measure the grit I use but in the 12 pound barrels I think I use about 1/2 to 3/4 cup of coarse grit. I am sure it is never the same because I just have a small scoop or cup that is in the grit container and I just put in what looks OK to me. When I get through running the coarse grit for the two weeks, I never want to see any or at least hardly any black grit left in the bottom of my wash pan. If I see a lot of grit left over as I clean out the rocks I feel that I have put too much grit into the barrel to begin with but since I do not measure I can't tell myself to cut back a tablespoon or so. If I do see some black grit in the bottom of the wash water, I try to pour off the water and then catch and save the black grit in a plastic butter dish/container and throw it into the next coarse barrel I set up. In each new load I try to add a couple of hands full of the real small BB sized rock to help with the tumbling action. Even two or three hands full of this small stuff just fills in between the rock so it doesn't really add anything more to the load. It just takes a little less water.
One thing I do with my pre-polish is to save it and reuse it for the next load. I also do this for the polish from a load. I keep the milk jugs separate and don't mix the materials. I just add a little more of the pre polish or polish to the next load. I may add a 1/4 to 1/2 the usual amount when I have some from a previous load. The jugs will usually settled some so the top is just water and I will pour off some of the water and just add the more solid (not a good word) slush (liquid polish) to the next load.
My pre-polish loads will have a lot of foam in the barrel while the Polish does not have the foam. These milk jugs will freeze in the winter time and then the stuff will run out on the floor. This happened in my dirty shop so it didn't do anything more than make a mess for me when they thawed out.
There have been a few times (2 or 3) that I did not get a good polish on a load of stones and I found out it was my fault. I was tumbling some of the material I received when my brother passed away. He had some stones that would not polish. (The last big one I gave to some kid at the bazaar.) These were all harder than agate, jasper and wood and all through the polishing step instead of polishing it would just scratch so the whole batch of stones just came out all cloudy. I knew it had to be something in the batch of rocks do I sorted through each stone to see if I could see something different about it. What I found were a few real heavy stones that had to be the culprit. I left these out and put the load of rocks through the 220, pre polish and polish again and they came out perfect.
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