To make your own concrete molds, you can build simple forms from melamine-coated MDF or wood for basic shapes, or create detailed molds using silicone rubber over a master object, often made from clay or foam, requiring release agents and backing supports for flexible molds. Simple household items like bowls or bottles can also serve as molds for unique shapes, while reusable options often involve creating a master piece, coating it with silicone, and then using that silicone mold for casting.
Silicone is the best material for making a concrete mold if you want to make multiple copies. It's a durable material that can withstand a lot.
Wood is the most cost-effective and popular material for concrete forms. Properly built wooden forms are lightweight, flexible and durable.
Supplies
Compared to commercial "form oils", Castor Oil based release is a great alternative. Diesel motor oil, WD40 and other harsh chemicals are commonly used within the construction trades to repel the tack of concrete to forms and molds. One caveat, Castor Oil is a known laxative. Ingesting might create some potty time!
A mold release helps so that your concrete will not stick to the mold when setting up. What kind of mold release should I use? A concrete mold release agent or a cooking spray like Pam works well. The cooking spray keeps your molds cleaner.
The lowest cost molding materials are ComposiMold and Impressive Putty. Instead of purchasing a new molding material every time you make a new mold, you can re-melt and re-use ComposiMold and ImPRESSive Putty.
Duplicating objects you love can be made easy by making a silicone mold and filling it with a QUIKRETE Concrete Mix.
Make Your Own Silicone Molds
This material is typically produced at a utility sluice pond site by dumping raw ash into the pond and allowing it to hydrate and harden into a working platform. Additional raw ash is placed on top of the platform in thin lifts, watered, compacted, and allowed to hydrate and harden.
The "90-minute concrete rule" was a standard guideline (ASTM C94) requiring ready-mix concrete to be discharged from the truck within 90 minutes (1.5 hours) of mixing to ensure workability and quality, but this rule has been updated, allowing for custom time limits to be set by the purchaser and producer, acknowledging modern admixtures that extend working time, though the original principle of limiting time to maintain quality remains crucial.
For building concrete forms, here's what you'll want to have ready; good straight 2x4s or 2x6s, 3/4-inch plywood sheets that aren't warped, 16d nails, solid wood stakes, tie wire, a reliable form release agent, your level, string line, hammer, and saw.
2 parts sharp sand to 1 part cement. Or: 3 parts mixed gravel and sand to 1 part cement.
Household Items You Can Use as Concrete Molds
Molds: Most concrete molds are made from urethane rubbers that resist concrete bonding. Paint: There are no natural bonding agents in paint. Oil: Oil or oiled surfaces create a film that prevents concrete from sticking.
Whether you are building a new fence, setting a mailbox or anchoring a basketball goal or play set, QUIKRETE® Fast-Setting Concrete is the ideal product for the job. With Fast-Setting Concrete there is no mixing or tools required – You simply pour the dry mix right from the bag into the hole, then add water.
These are the ingredients you'll need to make a mold out of silicone sealant: Water. Blue dish soap, like Dawn (Buy the cheapest kind possible, as you'll use a lot) 100% Silicone Sealant.
Insufficient injection pressure or speed, improper calculation of shot size, and inadequate heating of the plastic material are common causes of short shots. Complex mold designs with thin walls or distant cavities can also make it challenging for the molten plastic to fill the entire mold.
Using Silicone and Liquid Soap
Rust is difficult at the best of times, but removing rust from concrete can be especially challenging, as you're often trying to tackle a large area. If you need to get rid of rust from concrete, your best bet is to use some WD-40 Multi-Use Product, and some elbow grease.
Petroleum Jelly is a "Vaseline" type of paste release agent. Ideal for use between concrete and formwork, can be applied with cloth or brush or can be rubbed on by hand. Petroleum Jelly can be thinned with White Spirit, if a more liquid release is required.