A little about rock tumbling....

I remember being 5 and getting a Montgomery Wards rotary rock tumbler for Christmas.  The joy and amazement in a child's eye seeing rough rocks turn into smooth semi-precious wonders!  The only draw back was the month + it took from rough grit to polish.

As an impatient adult, I bought a Lot O Tumbler by Belt Inc. out of good ol' Owatonna, MN (15 miles away).  This vibratory tumbler can take 5 pounds of rock from rough to polish in 5 days.  Talk about immediate gratification.  Now for the really rough material like Lake Superior Agates and such, I leave them in rough 200 grit for up to a week to help shape and get past pits and heat/cold fractures (these agates are a billion years old-imagine all the cycles of heating and freezing they have undergone).  Anyway, the overall process is better for my need for immediate gratification than the old rotaries.

The barrel has a capacity for 5 pounds of rock.  I have found better results using less rock and about 1/3 of ceramic pellet filler.  The ceramic will hold on to the grit-making for more and better grinding action.  Ideally, the rock should be wet enough so that grit sticks to it and the action of the gritty rocks moving over each other takes off the extra rock material.  Too wet and the grit won't stick and the action is reduced. 

Typically, I will wash the rock I want to put into the load to get off obvious dirt and smutz.  I then put the rock into the tumbler barrel with the rocks being wet, but not dripping.  I then add 1/4 to 1/2 tsp of 200 grit to the mix followed by 1/2 cap-full of water (I use a full cap of water if I am not going to be able to check on and wash the rock at the 12 hour mark).  One word of caution, try to use rock that are close to each other in the MOH's hardness scale.  The hard stuff like agate (MOH's of 7) will disintegrate the softer stuff like Rhodocrosite/Chrysocolla with a MOH's of 3.5 to 4.  Hard learned lesson is that less is more-less water and small amounts of grit. 

I start with 200 grit.  Any lower number tends to not stick to the rocks and sits at the bottom of the tumbler barrel.  The nice thing about the Lot O Tumbler is that the action is more gentle than other vibrating tumblers I have tried-yet it gets the job done.  You can also watch the rocks and media going around because the to can be removed.  It sometime is a meditative thing for me and over time you can see small changes to the rock.

After 200 grit, I go to a couple of days of 600 grit.  You can do it with one day, but the longer it goes at this stage, the better the polish at the end.  Another hard lesson-more time and patience at the lower grits translates to a more amazing mirror finish at the end. 

Next comes a fine 1200 grit.  This has the consistency of powdered sugar.  The final is a day or two in Rapid 61 aluminum oxide polish.  No one really knows the secret of Rapid 61, as the company holds the recipe dear, but it produces an amazing polish.  At the end, I put a drop or two of dish soap in with the rock.  After an hour the rock gets pretty clean and there is far less washing and tooth brushing polish from out of the way crevices.  We cheat a little by putting the finished product (if harder material) into a small ultrasonic cleaner (about $45) 

I will post more later about rock tumbling and try to include some "Action footage" from the Rock shed in Keystone, South Dakota.  For now here is a picture.  We don't have a double barrel model but have 2 singles we have going most of the time.  The oldest one has run almost constantly for over 2 years!



Twin Barrel Lot O Tumbler on the left and Single Barrel Lot O Tumbler is on the right.