|On the right you can see an image of how rough rock will look before the process. The rocks are often full of sharp angular edges and there is little or no sheen showing – these are a little more rounded than usual. This is a typical image of the kind of rough rock you will find in lapidary stores / rock and mineral shops etc, dirty, chipped, unshaped and not very attractive to observe!
Take the rocks you have chosen and place them in the barrel. Remember to select a good range of sizes, with particular emphasis on those little bits and bobs which will do most of the hard work.
Fill the barrel until it is around three quarters to four fifths full – this applies to whatever sized barrel you are using.
Now pour cold water into the barrel until it just about covers the top of most of the top rocks. You can cover them (just about) totally if you need to, but I prefer to leave a little bit of rock showing because if I decide to take a look in the barrel at any time, I can just grab a rock which I can see – rather than messing around in the sludge!
Cold water is required because hot water can soften the materials (plastics) used to make the barrels, on certain models this could cause the lid to pop off whilst the water remains hot. Use cold water.
Now put in the grade 80 silicon carbide grit. Use around 1 heaped up table spoon of grit for every one pound of rock in the barrel. Don’t worry about exact amounts here, you really don’t need to. If you overdo it, then the tumble can go a little longer before all the grit is smashed up into inefective particles – thats all. If you don’t quite make up the full amount, don’t worry too much either – it simply means that this step of the batch may need to be repeated before you are satisfied with the shaping (more than one repeat of this (step 1) is often required anyway – so you will have plenty of time to buy more grit if you’ve run out).
On the right, you can see the blue line, this is the water line, the barrel is around four fifths full of rock, and the water level is covering most of the rocks, but leaving a few poking out of the top for me to grab hold of if I need to take a look inside during the run. You can see the silicon carbide grit floating on the surface tension of the water, and also resting on some of the stone. This is exactly what you want to be able to see in your project at this stage.
Now place the lid on the barrel and securely fix it into place. Double check it is tight – the last thing you want is for it to come off when you’re not around!
Before placing your barrel on the rails of the tumbler, power it up and let it warm up for a minute or two – just to get the motor going and bearings running smoothly. Follow any instructions on lubricating the machine over time, as this will add to its lifespan and ensire smooth running operation. Dry the outside of the barrel completely if it is wet.