Learn how to use silicone to make reusable molds for casting concrete.

SUPPLIES:

Plastic Bottle or Container
Recycle
To make a container for the silicone, use a plastic container that is just a little bit bigger than the object you want to copy.

Mold Star® 30
Available Online
Mold Star® silicones cure to soft, strong rubbers which are tear resistant and exhibit very low long-term shrinkage. Molds made with Mold Star® will last a long time in your mold library and are good for casting wax, gypsum, resins, concrete and other materials.


Quikrete Countertop Mix
Available at Home Depot
QUIKRETE® Countertop Mix is a super high-performance mix that is worth the price. It has no large pieces of gravel or aggregate, which makes it great for small intricate pieces such as lamps and vases. It’s easy to work with and comes in different colors. Most stores don’t carry it in-stock so call ahead to your local Home Depot to have it ordered for pickup.

TOOLS:

Hot Glue Gun
Available at Home Depot

Knife
Available at Home Depot

INSTRUCTIONS:

STEP 1: Cut the Bottle Into a Tube
Cut the top off of the water bottle and then made a second cut about 1/2" above the top of the object. This creates a plastic tube that's a little taller than the object.





STEP 2: Cut a Band
Cut a 1" wide band from the leftover piece of the water bottle. This band will be used as a support for the mold and the end of the bottle will be used as a cup for mixing the silicone.





STEP 3: Make a Bottom
Cut a piece of plastic out of the lid of an old plastic container.





STEP 4: Glue the Object to the Bottom
I used a hot glue gun to glue the object to the bottom piece of plastic.





STEP 5: Glue On the Tube
I used the hot glue gun to glue the plastic tube cut from the water bottle to the bottom base plate. I applied glue all the way around to make sure it was sealed and water tight.





STEP 6: Water Test
Pour water into the mold to make sure the silicone won't leak.





STEP 7: Use the Water
Silicone isn't cheap and can't be saved once the 2 parts are mixed together, so you want to mix the right amount. I poured the water into the cup I made out of the other end of the bottle and drew a line so that I would know how full to fill the cup with silicone.





STEP 8: Mix + Pour the Silicone
Mold Star® 30 comes in 2 parts that need to be mixed together in equal amounts. I filled to the cup and mixed the silicone before pouring it into the mold.





STEP 9: Remove the Object
Once the silicone has cured, cut away the plastic and remove the object. The silicone is flexible, but you may need to cut it a bit to get the object out. Try and cut the silicone in a place that will be minimally visible.





STEP 10: Prepare the Mold
Once you remove the original object, you'll be left with a detailed mold that's ready to be cast into a concrete copy. Slide the 1" wide plastic piece of water bottle over the silicone to hold the mold tightly together.





STEP 11: Mix + Pour the Concrete
I mixed and poured Quikrete Countertop Mix into the mold and made the mix a little more watery than usual so that it would pour easily into the silicone mold.





STEP 12: Vibrate the Mold
Tap and vibrate the mold to get out the air bubbles. I didn’t tap it long enough and my concrete piece had a few bubbles but still looked good.





STEP 13: Remove the Concrete Copy
After letting the concrete cure for 24 hours, I pulled off the plastic sleeve and removed the concrete copy. I also cleaned the mold with a toothbrush so it would be ready for another copy. The molds are quite durable and you can use them over and over as long as you keep them clean.









Good luck making your own silicone mold and concrete casted copies and please email, tweet or hashtag photos to @benuyeda, ben@homemade-modern.com or #homemademodern. For more detailed instructions, dimensioned drawings and different variations of the project, check out our soon-to-be-released book.

---