Namibian Picture Stone - Beautiful!
This image shows a 5-pound bag of Namibian picture stone tumbling rough, dumped into a colander and sprayed with water to reveal its full color. Click on the image for a larger view. Your tumbled stones are going to be beautiful shades of brown, cream and tan!
Namibian Picture Stone
(Tumbling or Cabbing Rough)
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Size: Mostly 1/2 to 2 inch pieces
Few jaspers fit their country of origin better than this! Namibia hosts one of the great deserts of the world, and this picture stone matches that scenery. It is a brown, cream and tan colored jasper that polishes to a beautiful semi-gloss finish. If you like deserts or the color brown, then you should enjoy this rough for producing tumbled stones or cutting scenic cabochons. A few pieces might have black manganese dendrites. If you are lucky, they might line up like bushes across a desert landscape.
We really like this material because of its color but especially because it shapes so easily in both rotary and vibratory tumblers. It rounds very nicely in rotary tumblers, and in vibratory the edges quickly smooth to produce interesting semi-angular stones. It is one of the few jaspers that will surprise you with its rounded shape when you dump it out after the first step in a rotary tumbler.
Namibian Picture Stone is sold in five-pound bags. Most pieces in the bag will measure between 1/2 inch and 1 3/4 inches in size (if measured along their maximum dimension). It averages between 10 and 20 pieces per pound - so you will need media or small-size rough when it is tumbled.
INTERMEDIATE Rock Tumbling Recipe:
Namibian Picture Stone (1/2 to 2 inches)
When tumbling this Namibian picture stone, two things should be considered:
1) More Time: Although this Namibian picture stone is a jasper and shapes nicely, it will require more than one week in coarse grit because of its size. In six-, twelve-, and fifteen-pound capacity barrels, two weeks might be enough to shape the rough to your satisfaction. However, in small tumblers of two or three pounds capacity, three or four weeks is often needed.
2) Media Needed: This picture stone jasper is in pieces that range between 1/2" and 2" in size. For that reason, we add about 25% ceramic media to fill the voids between the larger pieces of rough. The cylindrical shape of the ceramic media acts like a roller bearing and gives the rocks a smooth tumbling action in the barrel. The small pieces of media also deliver grit to all surfaces of the rough.
|Using Small-Size Rough Instead of Media: Some people use small pieces of rough instead of media. This can work well if your small rough meets two requirements: 1) the small pieces of rough must be blocky or rounded in shape to produce a good tumbling action - thin or flaky pieces will break up quickly and might not produce a smooth tumbling action; 2) the small pieces of rough must have a hardness that is equal to or greater than the rough that they are tumbled with - if they are softer they will tumble into mud before their job has been done.|
Recipe for Rotary Tumbling
Coarse Grit Step: Fill your tumbler barrel 2/3 full of rough and media (we use about 25% media and 75% rough). Then add 2 tablespoons of coarse (60/90) grit per pound of material in the barrel. Add enough water to cover the tops of the rocks. Run the material in coarse grit for 2 weeks. After two weeks check your material. If you are happy with the shaping, move on to the medium grit step. If more shaping is needed, clean the rough and start tumbling again with a clean barrel and fresh grit.
At the end of all steps in the rock tumbling process, make sure to clean your rocks and barrel to reduce the chance of coarser grit contaminating the finer grit steps. This cleaning is especially important before you begin the polishing step.
|How Many Weeks In Coarse? A little judgement will be needed because every barrel of rocks will be different. They have different sizes, different shapes, different compositions. And, tumblers come in many different sizes, different shapes, and run at different speeds. The human brain must be used to get optimal results. You will become wiser and get better results through paying attention and gaining experience.|
Medium Grit Step: Put your cleaned rough back into the barrel. Then add 2 tablespoons of medium (150/220) grit per pound of material in the barrel. If the barrel isn't at 2/3 full, add a little more media to bring it up to operating capacity. Add water until it is just below the top of the rocks. Tumble for one week.
Fine Grit Step: After clean-up, put the rocks back into the barrel using 2 tablespoons of fine grit (500F) per pound of material. Again add water to just a little below the top of the rocks. Tumble for one week. The rocks should now be smooth and possibly starting to get a slight luster.
Barrel slurry dumped down the drain will harden like concrete.
Polish Step: IMPORTANT: Make sure that your barrel and rough have been cleaned thoroughly. Any grit carried over from a previous step will likely ruin your polish. Place the rough in the barrel with two tablespoons of TXP polish for each pound of material in the barrel. Add enough water to almost cover the rocks and let it tumble for one week. You should have polished rocks at the end of this step.
Burnish If Needed: This material usually takes a great polish. However, burnishing it after the polish step can often improve the look of the stones. If you would like to try burnishing, full instructions can be found here.
Vibratory Tumbler Recipe:
1/2" to 3" harder rough
Coarse Grit (60/90 Mesh):
Coarse grit is not used in a vibrating rock tumbler.
Medium Grit (150/220 Mesh):
Due to the size of this material, it is recommended that you begin with a minimum of 30% ceramic media. The use of this media will aid in the tumbling action in the barrel and help deliver grit to all surfaces of the rough.
After you have your bowl loaded to the manufacturer's recommended level, add 1 tablespoon of grit for every two pounds of material, including the media, in the bowl. While the tumbler is running, slowly add water until the material has a thin coat of wet grit and the tumbling action is smooth and fast in the bowl.
Check the bowl every 8-12 hours to ensure the action is still good. If the action has slowed, add water a little at a time until the action is back to normal. If the mud gets too thick, you will need to do a complete rinse of the material and bowl. After rinsing, add fresh grit and water and start tumbling again. You are done with medium grit when you are satisfied with the shape and smoothness of the stones. Usually 4-7 days for us with this material. Give the material and bowl a thorough cleaning before moving on to fine grit.
Fine Grit (500F Mesh):
Place your material back in the tumbler bowl, then add enough polished ceramic media to bring the load up to the manufacturer's recommended operating level. Add one tablespoon of grit for every two pounds of material in the bowl. Then, turn the tumbler on and slowly add water until the material has a thin coat of wet grit and the tumbling action is smooth and fast in the bowl.
Open the bowl every 8-12 hours to check that the action is still good. We usually run fine grit for 48 hours. Thoroughly clean the bowl and material before moving to the polishing step.
Polish (#61 Rapid Polish or TXP):
Place the cleaned material back in the bowl. If needed, add ceramic media that has been previously polished, to bring the bowl up to the manufacturer's recommended operating level. Add one tablespoon of polish for every two pounds of material in the bowl. Turn on the tumbler and slowly add water. Stop adding water when the material has a thin coat of wet polish and the tumbling action is smooth and rapid.
Like the previous grit steps, open the bowl every 8-12 hours to check the tumbling action. Add water if it has slowed. We have found that 48 hours is usually all the time you need to get a good polish in a vibratory tumbler. Any more time than that, and you run the risk of damaging / bruising the material.
Burnish If Needed:
This rough will usually take a great polish. However, burnishing this material after the polish step can often improve the look of the finished stones. If you would like to try burnishing to see if it improves the look of your polished stones, full burnishing instructions can be found here.
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