Stone Master Molds Rubber Molds for Concrete, River Rock Flat Mold

Stone Master Molds Rubber Molds for Concrete, River Rock Flat Mold


  • Professional grade rubber mold will last for hundreds of pours
  • Create your own custom stone veneer for indoor/outdoor walls, etc.
  • Each of 5 mold versions has one-of-a-kind stones
  • NO RELEASE AGENT necessary
  • Matching River Rock corner molds available
  • Made in the USA
Free Shipping
Check out our quantity discounts on all products. Discounts will show in Cart.





2 - 3



4 - 6



7 - 99


Stone Master Molds River Rock Mold for Concrete

Stone Masters' River Rock Mold for Concrete duplicates a naturally river-worn, full-size stone, varying in sizes up to 10” in diameter, with thickness varying from 1-2.5" in the center.  River Rock is most often used on log cabins and coastal homes, on the outside and inside, not to mention it is gorgeous on fireplaces, too.

Additionally, each mold measures approximately 23.75" long by 11.5" wide, by 2.25" thick, and produces approximately 1.75 square feet.

Of great importance, our molds require NO release agent!   Save money, time, and clean up, as well as gaining an easy, clean release of face color pigments, unlike plastic molds, urethane molds, and silicone molds.

Available in 5 unique variations, with no stone repeats.  Also, matching River Rock corner molds are available.

Made in the USA, both materials and labor.

Manufactured Stone Basic Mixing Procedures Using A Pre-bagged Concrete Mix for your River Rock Molds for Concrete:

This is one suggestion for mixing the concrete for River Rock molds. Of course, there are many other instructions available online, including videos.

BE SURE TO USE A CONCRETE MIX THAT CONTAINS PORTLAND CEMENT. We recommend Sakrete Maximizer, as it has lightweight aggregate, is high strength, and yields more product, but there are many kinds you can use. Follow the manufacturer’s instructions for mixing.

If using pigment, add desired iron oxide pigment to mixer (100% pure, no additives). These can easily be found on Amazon, etc.

A plasticizer can be added to reduce the amount of water in the mix. Pour into the molds which may already have coloring additives… NO RELEASE AGENT NECESSARY. Vibrate molds to release air bubble.

Finally, cure the concrete in the River Rock molds for approximately 24 hours at the minimum of 70 degrees Fahrenheit before demolding. Higher humidity is desired. The River Rock molds for concrete can be covered with a tarp to retain more heat and humidity. Continue to cure demolded stones at 70 degrees or greater until ready.

5 reviews for Stone Master Molds Rubber Molds for Concrete, River Rock Flat Mold

  1. G


    These are pricey but worth it. Compared to other molds I’ve been trying, these are better and more durable.The rubber seemed cumbersome and heavy to me at first, but the finished stone pops right out; you don’t run into the same issues that you do with cheaper plastic molds. It’s much easier to get a result that looks much more like authentic stone.They’re also easier to clean off afterwards (which is something you have to consider–any residual concrete will result in a less authentic effect next time), because of the flexibility of the rubber.Also, the fact that they’re rubber, not plastic makes them a lot harder to break (and I’ve kinda tried. Lol).

  2. AC

    Aura Castellese

    I have used different products to make stones, but this rubber mold is the best of the best. I highly recommend this product. Do not be fooled regarding the hard plastic molds or some of the others being sold, which are made from lower-quality materials. Again, I highly recommend this product.

  3. SP

    Sharon P.

    The Veneer Stone Rubber Mold is so cool! I purchased in beginning of summer. Living at the shore, we’ve got sand, but no rocks to be found. So to edge along the back garden I began mixing Quikcrete from H.Depot in buckets. The mold has 7 diff. shapes. I bought the brown cement dye adding just a little each load so all rocks wouldn’t look the same color.(bottle says use all per bag of cement…I’ve used 5 bags of cement and still have dye left) I’ve made 158 rocks to date, looking to make more. Friends thought they were real rocks! Pour on batch at 7am, firm enough to pull out of molds by 2, next batch ready in 6-7 hours. I highly recommend!! *****

  4. MB

    Mari B.

    Easy to take out from mold

  5. G


    I use mold #5 to make river rocks for my custom paintings. My customers are amazed that these were made from a mold. I use white mortar mix for stucco Type S and they dry so very hard. For my rock painting I take out of after 48 hrs and round out the 90 degree edge to make it more complete rocklike. If I wait any longer then 2 days it’s more difficult to shape that rounded edge. Highly pleased and so easy. Love this rubber mold.

Add a review

Your email address will not be published. Required fields are marked *