We pay careful attention to all the minute details when making a mold or cast —mixing the materials in the proper way, de-airing them to get rid of pesky bubbles and applying an appropriate release agent for demolding the mold or cast. But how many of us actually take notice of the room temperature during the cure time of the mold or cast? We are mostly unaware of the toll that atmospheric humidity can take on our molds and casts. For instance, excess moisture in the atmosphere can delay or even impair the curing process of various resins, polyurethanes and latex mask rubbers. In fact, humidity is responsible for everything from tacky latex mask s and cloudy effect in clear resin castings to foaming in polyurethane rubbers.
TAP Premium Liquid Latex Rubber
Mold Making Liquid Latex – The Fibreglass Shop
To make a part out of latex, you first must make a plaster mold from the original, which can be plastilene clay, wax, plaster, or something else. You need the absorbancy. If the original has undercuts and fine details, you may have to destroy the original by digging it out of the plaster while the plaster is hot. A low-sulfur, waxy plastilene, or microcrystalline wax master will give you a the best plaster surface. The plaster mold will have to be dry before you cast latex into it.
Casting latex is a rubber that sets up as a result of water being absorbed into the plaster mold. Without fillers, the casting latex will set up with maximum flexibility. With the use of fillers, based on clay, varying hardnesses can be achieved. HX, andHX are prevulcanized casting latexes.
Latex makes the thinnest, most elastic and strongest mould of any type of mould making rubber. It can be pulled over relatively large undercuts when releasing the model without tearing. The number of coats can vary from 8 to 20, or more depending on the size and purpose of the mould. A simple mould of a chess set piece about 15cm high would normally take about 8 to 10 coats, each coat applied, then let to dry in a warm area until the white colour disappears before applying the next coat. About an hour or so between coats would be normal.