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Rock Tumbler Media Choices

January 24, 2021 Brian Dais

Tumbler media for rock tumbling usually refers to the fillers that are added to the rocks and polishing grit during the tumbling process.  Grit may be also referred to as media but it is usually separated into its own category – rock tumbling grit and/or polish. 

We will cover the two main types of media used as filler material for rock tumbling – ceramic tumbling media and plastic pellets for rock tumbling

ceramic rock tumbler mediaplastic rock tumbler media

Why Use Rock Filler Media?

Rock tumbler filler has several benefits that will improve your tumbling results.  The benefits include filling your barrel, cushioning your fragile stones, improving tumbling action and transporting grit to rock cervices.  Both plastic pellets and ceramic media will also quiet your tumbler, but plastic pellets are particularly suited for this.

Filling your Barrel

Filler is used to top off your partially full barrel, so it is at the recommended 2/3 to ¾ full.  A mostly empty barrel will allow the rocks to crash violently, causing possible breakage, bruising and scarring.  2/3 or so full will still allow the rocks and grit to slosh around to accomplish polishing but not allow the damage.

Cushioning

Both ceramic and plastic tumbler media will provide cushioning.  Even though ceramic is hard, it will still absorb some of the violent energy inside our tumbler.  Plastic pellets are great for cushioning even fragile stones.  We sell high impact polypropylene so it is soft to protect but is engineered for impact so it will last a long time. 

Improved Tumbling Action

Tumbler media will improve tumbling action and lead to better results.  It is recommended that you use a variety of different size rocks in your mix.  The small size of the media will help that combination to bring abrasive action into hard-to-get to spots in the mix.  The round shapes of the ceramic cylinders and plastic pellets will also keep your rocks tumbling instead of sliding along the surface of the barrel.  This is particularly important for flatter stones or stones with flat edges.

Transporting Grit

Both ceramic and plastic tumbling media will pick up grit and carry it into hard-to-reach places in the rocks.  The surface of the media will hold grit and rub it against the stones.  The smaller size of the media will help it get into nooks and crannies and smooth them off.  The more points of contact you can get between your grit and your rocks, the better.

Quieting your Tumbler

Both ceramic and plastic will quiet your tumbler by muffling the noise from the rocks mixing.  But plastic does have more sound absorption properties than ceramic does.

Two Main Types of Rock Tumbler Filler Media

Plastic:

Plastic has traditionally been used as the filler for rock tumbling, but ceramic seems to be preferred these days.  Plastic can come in many types but we recommend and sell polypropylene plastic pellets because they are tough and will last longer than other types of plastic like polyethylene.  We sell an impact-grade polypropylene because it will last even longer than standard polypropylene.  Also, when you buy plastic pellets, look for virgin pellets instead of recycled pellets.

Ceramic:

Ceramic is very popular as a filler since you can wash off ceramic and use it in the next step of tumbling.  They come in many shapes but we recommend cylinders with angled sides because they will get into the nooks and crannies of your rocks and rock mix and get grit to these areas.  Only use ceramic that is non-abrasive.  Ceramic filler is only meant to fill your barrel and protect and cushion.  It is not meant to do any abrasion – that is what the grit is used for.

Proper Usage of Rock Tumbler Media

Stages to Use

You can use filler in all the stages, if you like. 

With ceramic, you can just wash off the ceramic and use in subsequent steps.  However, fresh ceramic may have sharp edges so make sure it has been run in Step 1 and/or Step 2 to take off the sharpness.

Plastic pellets can also be used in all stages and although they can be washed off and re-used, you can only use it in the same step as it has already been used in.

Storage

Both ceramic and plastic media can be washed off, dried and stored for later use in a jar or bag.

Size of Rock Tumbling Media Used

Plastic pellets usually come in about the same size – 1/8” (3 mm) diameter.  This size works well to get into the rock mixture and perform the duties we talked about.

Ceramic cylinders are generally sold in 3 sizes/size combinations: large, small and mixed.

  • Large size cylinders are good for filling large empty spaces. The size we sell is 3/8” diameter x 5/8” long.
  • Small size cylinders are good for getting into tight spaces. The size we sell is 3/16” diameter x 3/8” long.
  • We also sell a ceramic mixture, which is by weight 50% small cylinders and 50% large cylinders. Many people like to use this combination to get the benefits of more fill with larger cylinders and the ability of the small cylinders to access the rocks.

Pros and Cons of Each Tumbler Media Type

Wear

If you buy high quality materials, both plastic and ceramic media should last you for several tumbler rounds.

Plastic tumbling media will eventually get beat up and need to be tossed.  Our Polly Plastics brand does prolong that happening since we use high impact polypropylene designed to take a beating but eventually it will wear out.

Ceramic tumbling media is hard and designed to not abrade quickly in a tumbler but that too will wear down over time and tumbling.  You can still use the smaller pieces of ceramic and add fresh ceramic cylinders to the worn ceramic but eventually they will wear away too much to be of any use.

Usability

Due to the fact that you can rinse off ceramic cylinders and use them in your next stage of tumbling allows for some convenience.  You can also reuse plastic rock tumbling pellets but you can’t use them in the next stage.  You’ll have to rinse them off and store them until you are repeating that stage again, in a future tumble.  That is because grit will become embedded in the plastic and although you rinse it off, you’ll never get it all out of the plastic pellets.

However, plastic has an advantage over ceramic tumbling media, in that you don’t have to worry about sharp edges marking your stones.  Ceramic tumbling media can have some sharp edges so it will have to be used in earlier stages before it can be used in polishing stages.  Or you’ll have to tumble it with coarse grit for a little while to burnish the edges.  Plastic has soft surfaces so there is no need to worry about marking.

Vibratory and Rotary Tumbler Usage

Ceramic media will work in both rotary and vibratory tumblers.  Plastic will work in rotary tumblers but is not recommended for use in vibratory tumblers.  So that is an advantage for ceramic tumbling media.

Cost

There is not a huge cost difference per lb. between ceramic and plastic.  But the same weight of plastic will fill more volume than an equal weight of ceramic.  So, you should need fewer lbs. of plastic to fill a void than when using ceramic media.

Should you go with Plastic or Ceramic?

There is no one answer to this question.  It is a matter of preference, so both are liked and used.

Some people like plastic and swear by its performance.  It is somewhat cheaper per volume but does need to be kept separate for use only in its one stage.  But it is great for cushioning stones and quieting your tumbler.

Others prefer ceramic and like that it can be washed and used in all the steps.  They also swear by its performance and will only use ceramic for their tumbling media.

So, it is up to the user to experiment with both and decide on what works best for them.

Other FAQs

Can I use Polly Plastics filler and grit in any tumbler?

Yes, our rock tumbling media will work with any brand tumbler.

Can I use Polly Plastics filler with any type grit?

Yes, our ceramic or plastic pellets can be used with any brand grit.

Can I use Polly Plastics filler and grit with any type rocks?

Yes, you can use our tumbler media with any type rocks.  We include instructions with our kits on how to get great results.

Polly Plastics Rock Tumbling Media

We sell both ceramic tumbling media and plastic pellets for rock tumbling.  Both types are designed to stand up to the harsh tumbling environment.  We sell 1.5 lb. packs of small ceramic cylinder, large cylinders and a mix of the two sizes.  If you use a lot of ceramic, we also offer 2 jar packs/3 lbs. total.

And we sell our high impact polypropylene pellets, designed for rock tumbling, in 1 lb. and 2 lb. sizes.




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