Our silicones and urethanes are very versatile and most may be thickened for brush-on molds as well as poured. For this mold we use Poly 74-20. Our Polyurethane formulas, such as 74 and 75 series, may be thickened with PolyFiber to create a brushable paste that may be applied by brush or trowel to a vertical surface. You can find PolyFiber as well as 74/75X accelerator in the urethane additives section. The shim technique we refer to in this video can be found on this DVD.
Once a 74-20 Brushed-on mold is made, there are a variety of mother molds or support shells that can be made over the completed rubber mold. Plaster and Hydrocal may be used to create inexpensive support shells. In this tutorial we use Hydrocal to create a support shell over a silicone mold. The same method works over Polyurethane rubber, but PartAll #2 wax is recommended to keep the plaster/Hydrocal from sticking to the rubber mold.
A resin mother-mold can also be made over a Polyurethane Mold. To make a resin mother mold requires careful release of the Polyurethane rubber mold surface. We released the 74-30 Mold using an application of Part-All #2 Wax and 2300 Spray Release. In this video we make a brushed-on resin mother mold over a Poly 74-30 Polyurethane Mold using thickened Poly 1512X Resin. The Poly 1512X resin was thickened with PolyFiber.
The Brush-on mold process is very useful in building restoration and similar projects where a mold needs to be taken off a wall or ceiling surface in a building or house. In this tutorial we explain the steps for making a fast, brushed-on mold with a simple (and fast) Plaster Bandage mother mold. We used our 5092 tin cure silicone with the red Fast catalyst. The 5092 was thickened to a paste consistency using the 5092 Thixo or thickener. Tin Cure silicone was used as there is very little risk of cure inhibition and cure inhibition is possible when working in an unfamiliar area with a pattern that could be contaminated. Clear PVA may be used as a sealer before Supralease PTR release is applied to make clean-up easy with warm water.
Our PlatSil Gels, such as PlatSil Gel-25 and Gel-10, are very popular for making fast, strong molds of all types of parts. PlatSil Gels may be thickened using TinThix thickener for brush-on applications. Since PlatSil Gels are translucent, silicone pigment may be added to aid in visibility and contrast of layers.
In this next tutorial, we show a slightly different approach for the mother-mold process. Here we use Gel-10 thickened with TinThix for the silicone mold and ArtKast Brushable for the mother-mold. ArtKast Brushable is an economical, easy-to-use, thixotropic (self-thickening) resin system that for making brush on mothermolds and large casts into silicone molds.
For larger props and monument molds, 80-30 silicone may be used. Our TinSil 80-30 is a tin cure formula and may be used over patterns that might inhibit the cure of our platinum formulas. Like PlatSil Gels, 80-30 may also be thickened with TinThix thickener.
In this next video we make a simple, 1 piece seamless mold of a skull using PlatSil Gel-10 thickened with TinThix. We created the rigid support shell with Plaster Bandages. This is a great, simple, and fast technique for molding small, relatively simple objects. We also used silicone pigments mixed into each layer to help track our progress. Adding pigment is optional but it does help in controlling the thickness of a brush on mold. You can find silicone pigments in our silicone additive section.
In the next tutorial we explain how to make a seamless Gel-10 mold with a resin support shell. This is a long one so get a cold drink and get comfortable. Gel-10 used in this video can be found on the PlatSil Gels page. 1512 resin we used for the support shell can be found on our resin page.
Another way to make a resin Mother Mold is by using our self-thickening ArtKast Brushable. In this tutorial we make a 2 piece resin shell over a brushed-on P525 silicone mold. We used Silver Vinyl Spray to protect the resin from the moisture in the water-based clay.
This helmet mold was made using a very simple process of PlatSil Gel-25 silicone thickened with TinThix an a mother mold made with Plaster Bandages. We used this mold to cast hollow, EasyFlo 120 helmets.
Another product we have for brushed-on mother molds is ArtKast Brushable. This is a self-thickening resin formula that starts as two liquids and becomes a gel after mixing. This is a great, low cost material for large light weight mother molds. ArtKast may be pigmented with PolyColor Pigments.