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Plastic Pellets for Rock Tumbling

January 24, 2021 Brian Dais

Plastic Pellets for rock tumbling are useful to add to your barrel and offer several benefits.  You will get better results due to filling a partial empty barrel and cushioning your stones, improving tumbling action and carrying grit to hard-to-reach places.  Finally, plastic pellets are probably the best tumbling media to reduce tumbling noise.

Plastic Pellets Media Benefits

Filler

Plastic pellets have been used for years to take up the empty space in a tumbler barrel.  A likely scenario is that you have some rocks to tumble so you put them in your barrel along with grit and water and see that the barrel is not full enough.  It is usually recommended to keep the barrel 2/3 full so that the stones won’t bruise, chip or break as they are tumbled.  Plastic pellets can be used to fill that empty void.

Cushioning

Plastic pellets are great for cushioning your rocks.  We sell high impact polypropylene for our plastic pellets for rock tumbling.  They are made to absorb impact, so they are one of the better, affordable plastics to use for the harsh environment.  But they are still plastic, so they are soft enough to cushion. 

Improved Tumbling Action

It is recommended that you fill your barrel with a variety of sizes of stones.  This mixture will improve the tumbling action by allowing more interaction between the sizes of rock so they will tumble together better.  Adding small plastic pellets will enhance that size mixture and help get the grit to where it needs to go.  The round beads will also help your rocks to roll instead of slide along the interior of the barrel.

Transporting Grit

Since plastic rock tumbling media is small (generally about 1/8-inch diameter), it is able to pick up grit and transport it to hard-to-reach areas of the stones like crevices and nooks.  You want as many points of contact between the grit and the rocks as possible.  For this reason, you should see better results when you use rock tumbling media versus not using it.

Quieting Tumbling Noise

We all know that tumblers can be noisy.  This is a particular problem if you live in an apartment or anywhere close to neighbors.  Plus, you probably don’t want to hear it either.  Plastic pellets are one of the best ways to minimize the noise made by the rotating barrel and crashing rocks.  It is analogous to tumbling a pair of tennis shoes in a dryer.  By themselves, they are incredibly noisy so throw some clothes in there too – to quiet it down.  Using plastic pellets will absorb the noise so you should see a noticeable difference between using and not using them.

One of the biggest advantages to plastic over other tumbling media like ceramic is its quieting properties.  We sell high impact polypropylene for our plastic pellets so they are soft enough to quiet and cushion but still can handle the impact of tumbling.

Proper Usage of Plastic Pellets for Rock Tumbling

Stages to use

You can use plastic pellets in any of the stages in rock tumbling.  But a disadvantage of plastic pellets over other less porous media like ceramic is that you can’t wash it off and re-use it in successive tumbling stages. 

You might find that you have to add additional plastic pellets after Stages 1 and 2.  This is due to the considerable amount of rock that is ground away during these early stages.  Adding more plastic will get it back up to the recommended 2/3 to ¾ fullness.

Re-using Plastic Pellets

Plastic pellets are tough, but grit particles will get embedded in the pellet.  So, although you can’t clean the plastic pellets completely, you can re-use them.  Just don’t use them in a stage that they were already used in.  Wash them off as best you can by using an old colander, let them dry and package them for use in a future tumble for the same stage they were previously used for.  Mark the bag or container so you don’t accidentally use them in a different stage.

Sharp edges

Plastic pellets don’t have sharp edges, so you don’t have to worry about doing any pre-polishing to knock off edges.  This is unlike ceramic media that may have sharp edges when you first purchase it. 

Storage

No special storage methods are needed for plastic tumbling media.  Allow it to air dry and then seal it up in a bag or container.

Types of Plastic for Tumbling Media

Suppliers sell all types of plastic for rock tumbling.  But the proper type is important.  We sell impact-grade polypropylene.  Polypropylene is a tough plastic that is even tougher and impact-resistant when it is impact grade.  Impact polypropylene will stand up to the tough action present inside a tumbler.  This means your plastic will last longer and will do a better job of protecting your stones.  Oftentimes, polyethylene pellets are used but these are softer and not as hardy as polypropylene.

Also, beware of vendors that sell cheap, recycled plastic that can be of any variety.  You can use a cheaper plastic for stuffing dolls or bean bags, but use a premium plastic for your rock tumbling.

Plastic Tumbling Media Shapes

Plastic pellets are usually round or cylinder-shaped.  The shape is not that important.  Regardless the shape, the pellets are small enough for carrying grit into hard-to-reach places among the rocks and also bringing grit to the crevices of your rocks.

Plastic Media Sizes

Most plastic pellets are about 1/8 inch (3 mm) in size.  Our Polly Plastics plastic tumbling pellets fit this standard also.

How Long will Plastic Pellets for rock tumbling last?

Plastic pellets should last through several rounds of tumbling but be sure to purchase pellets that can handle the high impact of tumbling.  Some companies sell the cheapest plastic they can find – buying off-grade or recycled material, often from China.  You should purchase high quality tumbling materials to ensure your results will be high quality also.

Does it work in all type tumblers?

Yes, you can generally use any brand plastic tumbling pellets with any brand tumbler.    However, it is recommended to use plastic media only with rotary tumblers.  Plastic media is not recommended for vibratory tumblers.  You should use our ceramic tumbling media if you are using a vibratory tumbler.

Can I use it with all Types of Rocks?

Yes, plastic tumbling pellets can be used with any type of rock.  The plastic is soft enough that it will not damage any stones.  Plastic pellets are a great choice of media if you are tumbling stones that are softer.

Can you use it with any brand grit?

Yes, you can use plastic tumbling pellets with any brand grit.  But we recommend using premium grit like the type we sell.  We guarantee a beautiful polish because we control the quality of our grit and have a proprietary Stage 4 final polish.  Our final polish is properly sized and have maximum surface area that has been proven to give a great finish.  You don’t want to invest 30 days tumbling and not be satisfied with the results.

Why aren’t my finished rocks shiny?

If you use our 4-Step Kits with plastic filler and follow the included instructions, you should get great results.  Some things to consider if they aren’t shiny:

  • Don’t overfill your tumbler with rocks and media. You should not fill it over 2/3 to ¾ once everything is in there.  If you do, your rocks won’t slosh around and get abraded by the grit.
  • Tumble rocks with varying hardness. If you use a combination of hard and soft stones, the hard stones will abrade the soft stones.  Even in the polishing stage, the harder stones will dull the surface of the softer stones.  Consult a rock identification guide to learn the type and hardness of the rocks you are tumbling.
  • Tumbling pitted rocks. You can tumble rocks with indentations, but it is hard to get polishing action in deep recesses, so the rocks will be duller there.
  • Using the improper amount of grit. Many people use too much grit, thinking that more is better for shinier rocks.  We recommend 1-2 TBS, depending on the Step.  Follow our instructions for good results.
  • If all else fails, burnish your stones by adding a few slivers of Ivory soap with the rocks. Wash everything off after Step 4, add just the soap, rocks and water together and tumble a day or so.  The soap will add gloss to the surface of your stones.

Polly Plastics Plastic Tumbling Media

Our plastic tumbling media has been proven to work great for all types of rotary rock tumblers.  We offer 1 lb. and 2 lb. quantities to improve your tumbling.  We also sell a popular kit that contains the 4 stages of grit you need plus plastic tumbler media.




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