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Posted in response to Coarse grit problems from Cheryll on November 24, 2014 at 09:04:38:

Re: Coarse grit problems

Hi Cheryll you are in to big a rush.
I'll send you some instructions I have shared several times on the rock net.

Tumbling

Many different art forms

There many different aspects or art forms in the lapidary hobby. I have been involved in the hobby for many years (since 1971) and haven’t had experience with even half of them. One of the ones I really enjoy is tumbling. There is nothing like placing some stones in a container and some time later removing some beautiful gems.

First exposure

Tumbling is how most people get their first exposure to the lapidary hobby. They get a hold of one of those small single barrel units that claim to give you finished stones in a couple of weeks. Like nearly everyone their in a hurry.

Three important things

There are three important things to remember when you decide you would like to try to tumble some stones. The first and absolutely the most important is patience. The second and almost as important is the stones you are trying to tumble or (garbage in garbage out). Lastly if you going into it for the long haul you’ll need some heavy duty equipment.

Patience

Starting with patience it will take from six to eight months to go from rough to finished stones. I have in the past tumbled sapphires for over three years. I clean a barrel once a month. I have three twelve pound barrels going at a time with coarse (60-90) grit and that is all the time.

Like stones

It is important to pick stones of equal hardness (example I would not place Obsidian with agate) especially in the polish stage. The Obsidian will end up with scratches all over it, but especially on the edges.

Coarse Run

I fill a barrel about a third to half full of rough stones. For a twelve pound barrel I use eight level table spoons of coarse silicon carbide (60/90). Than just cover the stones with water. I fill the rest of the barrel up with cubes of stryo-foam. The stryo-foam works as a cushioning agent to keep the stones from banging to hard together until a slurry builds up and keeps the stones from getting chipped.

Inspect each and every stone

The next step with the stones that have been in the coarse grind for a month. You have to inspect each and every stone for cracks or holes. If there are even a tiny crack or hole grit can hide in these cracks or hole and come out in the polish stage it will rune the polish. I run my finger nail over a suspected spot if it catches the stone goes back for another thirty days is coarse grit. This first step in coarse grit can take at least two to three months. I take the stones that passed muster in coarse grit and place in a box until I have enough to go into the next grit (220).
One additional foot note, but very important “The Worst Enemy Of Polish is Commination that is grit that hides in those cracks and holes ”.

Garbage in garbage out

Going back to the second item I mentioned (Garbage in garbage out) stones that have a number of small holes or cracks that look like they will run all the way trough the stone such as some moss agates. These stones are really a waste of time for you to try to tumble because of the holed and/or cracks where grit can hide and mess up your stone in the polish stage.

(220) Run

Once I have enough stones that have passed inspection from the coarse grit I put these stones in a barrel. For the remainder of the steps I use a smaller barrel or (six pounder), but you can use what ever you have available. I fill the barrel a third to half full of stones. For a six pound barrel I use four level table spoons of silicon carbide (220). Than just cover the stones with water. I fill the rest of the barrel up with cubes of stryo-foam. The stryo-foam works as a cushioning agent to keep the stones from banging to hard together until a slurry builds up and keeps the stones from getting chipped. I run this and all the other runs for thirty days. After the barrel has run for thirty days clean the stones and it is a good idea to check the stones to make sure a hole or crack did not open up while your stoned were tumbling in (220).

You have to decide (400 & 600)

The next step or steps is a matter of how good of a polish you would like to end up with. I personally go trough both (400 & 600) grits with the same procedure that I went trough with (220), or you can stop at (400).

Polish

The last and final two steps are the polish step in two parts. You really should take a little extra time to check out the stones to make sure the stones are clear of all defects. Than place them in a barrel the same as before, but this time about half the amount of the water that you used in the earlier steps. Now for the polishing agent I have used a number of different types of polish in the past (even Spick & Span the powered type) with good results. You can try different types of polish and see which one works best for you. But instead of using stryo-foam I use plastic pellets as a cushioning agent with a little squirt of dish washing detergent. Be sure to save the plastic pellets they are reusable. After you have run the stones for thirty days in the first part of the polish step. Clean the stones and the plastic pellets and place them back in the barrel along with 1 ½ oz. laundry detergent (the dry type). I have used both (Tide & Cheer) both work well. You will only need to run them in the laundry detergent for 2 or 3 days and your done.

Barrel speed

One last thought the speed your barrel revolves at, it almost can’t be to slow. If you have away of slowing it down you will be happier with the results.

Well that is about it.

From Bob Place - December 12, 2014 at 08:08:11
Email:

Message: 71002



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