thanks, more questions

FYI - you can just reply to one of your threads to ask further questions. We'll see it and help you out. This isn't the most active of forums, where things will get lost easily.

It's a big "no-no" to re-use pellets from one stage to the next. The grit gets embedded in pellets and it eventually releases to cause problems. (You can see this because they turn greyish) Particularly in the polish stage, any source of contaminination can be enough to cause a failure to polish - the size of the grit at that stage is so minutely small that more course grit will cause scratches that will affect the rock's ability to polish. It's much simpler to just dedicate pellets to each stage, although you can save them and reuse them in that same stage for future batches.

Like I mentioned in one of my replies previously, I think you'd be better served by learning on a batch that you know will polish. That means one of the tried and true jaspers, agates, quartz, chalcedony, etc. If you don't know what that looks like in the field (hounding), or you don't have a means of testing the hardness, you will get better results from purchasing these types of rocks to start.

Major holes, fissures and cracks are a source of contamination for future stages, which can cause issues with that stage. (Plus, they detract from the end quality) While it's not impossible to move on from stage 1 with such defects, cleanliness becomes very important. The concept of "burnishing" between stages helps very much with this. Basically, the idea is to run the rocks in something like Borax for 2 to 24 hours...but even that isn't a guarantee. It's better to run stage 1 until the rocks are completely ready...absent of any blemishes.

Hardness is a scale that measures how "hard" rocks are. The concept is that different minerals/rocks/materials/etc have different levels of hardness. There are two known measures for this - a relative scale called the MOHS scale and is based on specific minerals that have been measured and act as a reference point. There is also an absolute scale called the Knoops scale. Pretty much everyone has agreed on the MOHS scale in this type of work. Different materials can be measured against this scale - for example, quartz has a known value of 7. Flourite has a known value of 4. The scale is from 1 through 10...10 being a diamond (hard), 1 being talc (soft), aka talcum powder. Other materials can be measured for their hardness against these reference minerals. Quartz/jasper/chalcedony/agates/etc have a MOHS hardness of 7 and will polish well...that's why they're generally recommended. Generally speaking, rocks that are MOHS 6 or harder will polish, but there's exceptions to that of course. You want all of the tumbling rocks to be of the same hardness...or at least fairly close Otherwise, the harder ones will beat up the softer ones...and you either won't get a polish, or worse, the stones become damaged. There's a fair amount of info here about hardness and also a lot of information on the web.

As far as size, it depends on the tumbler. The point is to have a good distribution of sizes, from pea sized up to the size your tumbler can handle. It's better to have more medium and smaller rocks than large rocks, mainly because the surface contact between the rocks is more efficient and the grit is able to make more contact. For a 6lb tumbler, probably 2 or so inches would be your biggest...and you'd only want 1 or 2 of those tops. The rest should be smaller, with a good balance, and generally 1/4 to 1/3 or so should be small rocks.

I'd recommend spending some time looking through the old forum posts here in the tumbling section. There's a LOT of information and it will answer questions that you have even yet to formulate. I found this place as a fairly experienced tumbler, but I've learned more in my six months here than the 10 years of tumbling that came before it. You might also desire picking up the book, "Modern Rock Tumbling" by Steve Hart. He explains the process very well, covers all the aspects and it's well organized. There's nothing in there that you couldn't learn here, for free, but for some people, it's best to just pick up a book.

Phew. Hope that helps.

Thanks so much, OK, if we find the hardness is right for some of these to go together, what about the porus ones...most of them have small holes covering them...is this what the tumbling removes? Or will it make the holes even bigger?
I am frustrated that the store, which is awesome and helpful, told me it was OK to use the pellets from one grit to the next. No more doing that. I want to avoid the pellets all together this time, although now that it is warm enough to use a hose and screen instead of the kitchen sink and bowl and strainer, this won't be such an issue.....trying to clean them in the warm kitchen while not letting the water go down the drain is hard. I think we are going to buy some rocks tomorrow and try them, then go with our own batch. Thanks so much. I will dig around on past posts for more help.

Porous rocks likely won't tumble polish. The 60/90 step should remove all pits, cracks, etc. You should check the 60/90 step every week or so and remove any rocks ready to move on. Add more rough and keep going until you have a complete 2nd step batch. Moving defective rock to next steps results in (maybe) shiny rocks full of pits/cracks, etc. By the way, I've never had a separate barrel for polish. Clean the barrel well before going to fine grit and again before polish works fine. If you run until grit is completely broken down you can just rinse rocks/barrel and load up next grit between 60/90 and step two. If the step two grit is broken down you don't need to worry much about really scrubbing the drum before step 3 but I usually clean it out a little better anyway.

Another point, make sure you "burnish" for 2 to 24 hours between the pre-polish (e.g. 400 to 600 grit) and the polish stages. Borax is a good material - but ivory snow or other non-sudsing soap will do. I like borax because it's made from rocks...seems fitting. This will insure that the rocks are truly clean and free of contaminants before polish - you'd be surprised at how much "stuff" comes off the rocks.

Here's our very own tutorial (www.rocktumblinghobby.com/cycle/cycle.html) that was put together. It covers a lot of the details, but certainly not every possible thing.

Like others have said, ceramics can be used in lieu of pellets, or as a supplement, and they can be transferred from stage to stage with a good cleaning. They're more expensive initially, but provide better long term results. I've used pellets for a number of years, and it's served me fairly well, but I do want to experiment.

And yes, 2/3 to 3/4 is where you want to be. I've found it helpful to make a little skewer stick with the precise 2/3 and 3/4 marks so I can be confident that my load is where it needs to be. The barrel load and water level is important to creating a consistent slurry from batch to batch.

As far as checking hardness, if you want to try your hand at this, common materials can be used. For example, if it can be scratched by regular window glass, you know it's MOHS 5.5 or below. If it can be scratched by quartz but not glass, you know it's from 5.5 to 7. If it can be scratched by sandpaper, but not quartz, it's from 7 to 8. If it can be scratched by a steel file, but not glass, you know it's from 5.5 to 6.5. And lastly, if it's not scratched by a steel file but is by quartz, you know it's from 6.5 to 7. Other known materials could also be used, but this is what I've researched/found/used.

It's important to make sure you give it a good attempt at a scratch with sharp materials and that what you're viewing is truly a scratch and not just a streak. Wiping the material off post scratch and checking with a 10x loupe is very helpful. I found this testing method difficult sometimes, particularly on lighter colored rocks, because there were times where I couldn't tell if it was a scratch or a persistent streak. For that reason, I recently invested in a "Hardness Kit" - which has turned out to be mighty helpful. It's not a cheap investment (about $70 + shipping) and is probably an investment to be made once you're sure you're hooked on this hobby. This tester has shown that some of my previous testing using the materials above were not 100% accurate.

Tumbling is really a fun hobby, but it's not just as simple as tossing some grit and water in a barrel and letting it go. There's a lot to learn and I would argue that this is what makes it interesting.