Silicone forms recently began to enjoy simply huge popularity. They are made very simply. If desired, they can be made even with their own hands. The service life of them is very long compared to, for example, plaster. However, of course, the quality form can be made only from a material with good performance. What qualities should liquid silicone have for forms and what should I look for when buying it?
Types of silicone and master models
Of course, when buying a material for the manufacture of forms in the first place should pay attention to its technical characteristics. Today, only two main types of silicone are produced: coating and casting.
And for that, and for other material in the manufacture of forms, master models can be used both from metal and wood, and from plastic, cardboard or even just paper.
This type is suitable for making molds very well. This is a very viscous silicone applied to the master model with a special brush. As an example of such a material, one can cite the heat-resistant auto-seal ABRO.
It is also a good material for making molds. When using it, the master model is installed in the flask and poured from above. Liquid silicone for the forms of this variety consists of two components: a hardener and a base. Before pouring them thoroughly mixed, and then placed in a vacuum chamber to remove air bubbles. A very popular material of this type is, for example, Pentelast-708C.
What characteristics can be considered the most important when choosing a material such as liquid silicone? For the manufacture of molds, in principle, almost any of its varieties are suitable. However, pay attention to some indicators when buying is still worth it. The most important parameter characterizing the quality of silicone is the coefficient of elongation. In modern materials, this indicator varies in the range of about 200-1300%. The higher this figure, the stronger the hardened silicone can stretch and the greater the number of castings the shape made from it can withstand.
In practice, 700–800 percent one- or two-component liquid silicone is commonly used. For mold production, it usually fits just perfectly. Products made from a material with such a coefficient of elongation can easily withstand up to 80 castings. This indicator may be smaller or larger, depending on the complexity of the configuration of the master model.
It is also an important indicator that has a huge impact on the quality of the finished form. Filling liquid silicone for molds has a very low viscosity. In the process, he easily fills the smallest recesses of the master model. And therefore it is advisable to use it for the manufacture of forms of very complex configuration.
Measured viscosity in CPS. For casting materials, this indicator usually does not exceed 3000 CPS. For comparison: water has a viscosity of 0 CPS, sunflower oil - 500, honey - 10,000.
In addition to viscosity and coefficient of elongation, when choosing a silicone one should pay attention to:
Working time. The higher the rate, the longer the material retains its viscosity.
Polymerization time. This feature is also quite important. It shows for what period of time the cast form is gaining the stated coefficient of elongation.
Two-component liquid silicone for mold production usually hardens and polymerises longer than viscous. This can be attributed to the benefits of the material. After all, when working with him, the master does not need to hurry anywhere.
How to apply
Liquid silicone is used to make the molds as follows.
The master model is fixed on the stand with a droplet of superglue and coated with a special release agent. At home, it can be, for example, petroleum jelly or motor oil.
Stand with the model is secured to the flask. The latter can be done in almost any material: wood, clay, plastic, etc. Disposable flask is made of paper. Its height should be twice more than the future form. The fact that in the process of system evacuation the silicone is very foam. One of the walls of the flask should be removable.
The evacuated compound is poured in a flask in a thin stream. This is necessary in order to get as little air as possible into the liquid material.
Flask is placed in a vacuum unit for 1-2 minutes. Reprocessing is necessary in order to completely remove from the silicone all the air that has entered it during pouring.
Stiffens the form for about 5-6 hours. The final polymerization occurs in three days. At the final stage, the form is removed from the flask and cut in half. After that, the master model is removed from it.
Viscous silicone molds
In this case, a slightly different technology is used. Opoku in the manufacture of forms of silicone is not used. The master model is simply coated with material using a special brush in several layers (2-3 mm each) with intermediate drying for 2-3 hours.
Liquid silicone for molds: price
The advantages of this material include not only the ease of manufacture of forms. He deserved great popularity including for its low cost. The price of high-quality silicone can vary only in the range of 450-750 rubles.
In specialized stores or on the Internet should look for silicone, designed specifically for making molds. The fact is that today various types of this material are produced. For example, silicone liquid fishing is sold. It is used to lubricate the braided threads on the gear, which prolongs their service life and increases the casting distance. Of course, such silicone is not suitable for making molds.
How to make at home
In order to make liquid silicone for molds with your own hands, you need to buy ethyl alcohol and liquid glass. You will also need a plastic bottle and a wooden stick. Since the components of silicone are quite caustic materials, thick rubber gloves should be worn. The manufacturing procedure itself is as follows:
In a plastic bottle in equal parts pour liquid glass and ethyl alcohol.
The mixture is thoroughly mixed with a wooden stick.
After it thickens, it must be removed from the bottle and carefully stretched with your hands.
Silicone, prepared in this way, resembles plastic sticky rubber, and any shape can be made from it.
Silicone molds for the oven
Of course, for the manufacture of such castings to use environmentally hazardous materials can not. In this case, liquid silicone for molds is made a little differently:
Three tablespoons of potato starch are poured into a glass of yoghurt.
Pour the same silicone sealant in the same quantity.
Stir all for ten minutes.
From the silicone thus prepared it is easy to make a simple baking dish. Before pouring the dough, it is necessarily oiled with vegetable oil.
Use of silicone molds
So, for making molds, liquid silicone is often used. The use of products fashioned from "starch" material allows you to bake original cakes, cakes, etc. And how are the forms of ordinary silicone used? Most often they are used for the manufacture of beautiful products from all sorts of two-component fills. Any large items are usually not made using silicone molds. Therefore, the usual medical syringes are used to mix the components of the fillings at home. Then they are tinted with a dye droplet and poured into the mold through a stretch-stretched injection hole.