EZ~Mix® 40 Brushable Urethane Rubber: The Easiest To Mix Off All 'Off-The-Shelf' Brush-On Systems
New EZ~Mix® 40 brushable urethane rubber is a liquid / liquid system. Parts A and B are very low in viscosity, making it easy to measure 1A:1B by volume and the easiest to mix of all brush-on systems (perfect for novice mold makers).
It has a good working time of 18 minutes (at room temperature) and a re-coat time of about 60 minutes. If you want to thicken the rubber to make a cut shim, you can use Cab-O-Sil or similar fillers.
Unlike Rebound® 25, you can apply EZ~Mix® 40 to a sulfur clay model (model must be sealed with Spray Shellac, followed by a release agent).
Beware of "mass" with this product - Unlike the other brushable rubbers, this product has a slight exotherm to it and is mass sensitive. That means that large amounts in a mixing container will gel more quickly. Also, the working time for this product will be drastically reduced in warm environments.
EZ~Mix® 40's tear strength is better than competitive products on the market. But like these competitive products, cured rubber will "unzip" if a notch tear develops in the rubber. Brush-On™ 40, 50 and 60 have much better overall tear strength.
The secret for success in using this or any brush-on rubber is to apply a thin first layer (detail coat) to minimize air entrapment and capture all detail from the model's surface.
The original model is made of urethane plastic. It is hot glued to a working surface.
The model and board are sprayed with a coating of Ease Release® 200 release agent.
EZ ~ Mix® 40 Parts A and B are measured in equal amounts by volume.
Wearing rubber gloves is recommended.
Parts A and B are combined in a mixing cup. So-Strong Red color tint is added to color the rubber. This will ensure thorough coverage over the white model.
Begin brushing the EZ~Mix® 40 onto at top of the model and work your way down.
The first layer is applied thinly to ensure capture all detail. A 3 in (7.6 cm) flange is created.
After 1 hour, the rubber is tacky. A second batch of rubber is mixed and applied (untinted).
After the 2nd layer is 'tacky', Parts A and B are mixed with Cab-O-Sil to thicken the rubber.
The thickened rubber can be used to create a 'cut shim' and fill in undercuts.
So-Strong color tint is added to provide contrast to the cut seam.
The cut seam is applied along an edge to minimize and seam that may be reflected in finished castings.
The cut shim is extended to the outer edge of the flange.
Another batch of Cab-O-Sil rubber is mixed and used to further build up the cut shim.
A 4th (final coat) of untinted EZ~Mix® 40 is applied. All layers are then allowed to cure for at least 16 hours.
After the rubber is fully cured, the flange is trimmed to help the mold register with the support shell.
Clay is used to form parting shim, dividing the support shell into two halves.
Aluminum foil is placed over the mold and clay shim so the Plasti-Paste® shell won’t adhere.
Plasti-Paste® plastic is mixed and applied over the first half of the model. Allow 1st half of shell to cure for 90 minutes.
After 1st half of shell is cured, the clay shim is removed. Foil is used to cover the 2nd half of the rubber mold and cured Plasti-Paste® to prevent adhesion.
Plasti-Paste® is mixed (green pigment added) and applied forming the 2nd half of the shell.
When the 2nd half of the shell has cured, both halves are removed from the rubber mold.
An exacto knife is used to cut through the thickened shim for easy removal of the rubber.
The EZ~Mix® 40 mold rubber has perfectly captured all detail from the model.
The supprt shell and mold are reassembled and placed into a bucket for stability during casting. Make sure everything is level.
EZ~Mix® 40 is a urethane rubber and requires a release agent to stop the plastic from sticking.
Tinted Smooth-Cast® 300 is poured into the mold. The plastic cures quickly: demold in 15 minutes.
The result is a perfect reproduction, with a mold and support
shell that can be used repeatedly.