incult
off to a rocking start
Member since October 2010
Posts: 24
|
Post by incult on Oct 3, 2010 22:54:03 GMT -5
Hi everybody!
I'm new to this hobby. I bought this Thumler tumbler and for my first batch I tried to follow the manufacturer instructions and the grits that came with the tumbler. I also got some extra grit, so I took my time and I ran the corse step for three times, selecting only the good stones to move to the fine grit. When I had enough pebbles to fill the barrel I ran the tumbler with the fine grit. Everything fine so far, except that the fine grit removed a little to much than I wanted from the stones.
After one week with the fine grit I went to the next step, called by the manufacturer prepolish. I was supposed to run it for 3 days. Today I opened the barrel and I'm a little disappointed. Most of the rocks have pits which they didn't have before this prepolish and I have no clue what might have happened.
I need some help to figure it out. Can it be the grit? It was only saying "Prepolish" on the bag, so I have no idea what material it is. Can it be the plastic pellets that I used? Or maybe the pits were there the whole time but were filled with grit so I didn't see them (I don't think that's possible since I inspected them very carefully)...
I hope there's someone who can give me an idea of what hapened and how to avoid this problem in the future. Thank you guys in advance.
:help:
Incult
|
|
|
Post by susand24224 on Oct 3, 2010 23:22:55 GMT -5
Do you know what kind of rocks you were tumbing? Some rocks just get pits, period, and it may just be coincidence when they showed up. I agree with you that you likely would have seen the pits if they had been there before. Plastic pellets will not cause pits. Do you have any shattering of the rocks? I'm sorry that I'm answering your questions with more questions, but it does seem odd.
If the pits are small, you can go back to coarse grit. It is pain to start over, but all is not lost.
Susan
|
|
quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,341
|
Post by quartz on Oct 4, 2010 8:12:40 GMT -5
Many people use ceramic shapes and plastic pellets as filler and padding, with apparently good success. We prefer leather scraps, works fine for us. The stuff gets pretty slimey, but we have good result, if all else fails, give it a try. Use anything available, other than dyed or really thin split leathers; pieces about 1 to 1 1/2" in dimension. Good luck.
|
|
|
Post by johnjsgems on Oct 4, 2010 8:37:58 GMT -5
A pretty common problem is people start with 2/3 barrel and reduce every step until the load is too small by step three. The rocks fall rather than roll causing chips, fractures, and pits. Also, some minor problems don't show until you start to polish. Plastic pellets (separate pellets used each step) are used as a cushion. I like ceramic media better and you can add more to mix as needed.
|
|
incult
off to a rocking start
Member since October 2010
Posts: 24
|
Post by incult on Oct 4, 2010 11:37:23 GMT -5
Thank you guys! Susan, here's a picture. It's not mine, but the stones are similar to what I have, so I guess the pitted ones are some type of quartz. I had a mixture of beach pebbles, and it seems that the ones similar to the stones I marked, got the pits. Again it's weird because I didn't notice the pitting after the fine grit. they all seem fine. I'm thinking that maybe a chemical reaction happened between the "prepolish" grit and the whatever the black part in quartz is...do you think is possible? You asked about shattering...there was a couple of rocks that were chipped, but one had a crack from the previous run and I was hoping it will make it through and the other one the novo, but nothing major. And again, the rocks don't seem chipped, more chemically attacked on the black spots. Attachments:
|
|
|
Post by jakesrocks on Oct 4, 2010 12:05:59 GMT -5
The rocks you have marked as pitted seem to be a granite material. I'd suggest that you avoid this type material in the future. Granite is made up of several minerals. Some softer than others. The soft stuff will chip, leaving the harder material, and pits. Also, not all granite is created equal. In some types the grains are very loosely cemented together. They will crumble with tumbling. If you're collecting beach or river pebbles for tumbling, look for the ones that seem to be made up of one solid material. As you learn more about tumbling, you'll learn how to tumble softer materials.
|
|
|
Post by deb193redux on Oct 7, 2010 8:57:21 GMT -5
I agree about the granite. There may also be some highly altered jasper there, when parts of the rock have lost silica and started to become softer.
Others like the whitish one down front would be a quartzite and not a quartz. This is common with beach and river stones.
I also think these rocks are much softer than you think. Generally the only time you can visibly see material loss is in the course grit. IF you "fine" was still kind of course, e.g., 220, then you could still get further removal of material - but should never be "more than you expect". Fine grits should only sand the shape that is there and should not be able to grind much - except on softer stones.
Overall this kind of batch is very difficult, and should be attempted after good skills have been learned using highly uniform well silicified agates and jaspers that are fracture free. Then learn to deal with specific problems.
You also do not mention the color/type of pre-polish. Were all the grits gray and the pre-polish light tan or white? If so, it is likely the pits were there all along and you only saw them when they got filled with light colored slurry.
|
|
gemhunter
starting to spend too much on rocks
"Rock On"
Member since November 2009
Posts: 243
|
Post by gemhunter on Oct 7, 2010 12:48:04 GMT -5
:)Hello, I agree, for whatever that is worth ;D, get some agates, I found they are the best to start with. Also :2cents: buy a couple more barrels with lids and belt, about $20 each, when you can. Label them coarse, fine and polish, that will help keep the stones from being contaminated. Keep on tumbling. Ed
|
|