Stone Master Molds Rubber Molds for Concrete, Keystone Mold, 12″L x 7.75-4.75″W x 2.5″D

Stone Master Molds Rubber Molds for Concrete, 12" Keystone Mold

Stone Master Molds Keystone Mold creates a keystone with a chiseled stone texture on the front and smooth sides. Each keystone is 12" long, 7.75" wide at the top, 4.75" wide at the bottom, and 2.5" thick.  If needed, you can pour it thinner, as desired.

Moreover, save money and create your own custom colors using our professional quality rubber keystone mold.  This professional quality mold can be used for hundreds of pours with proper care!

Our molds require NO release agent. Consequently, this will save you money, time, and clean up, as well as easy, clean release of face color pigments, unlike plastic molds, urethane molds, and silicone molds.

Made in the USA, both materials and labor.

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

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

MOST IMPORTANTLY, 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.

In addition, 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. Next, vibrate molds to release air bubble.

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