Silicone molds have recently become very popular. They are made very simply. If desired, they can be done even with their own hands. Their service life is very long compared to, for example, gypsum. However, of course, a quality mold can only be made from a material with good performance. What are the qualities that liquid silicone should have for molds and what should I look for when buying it?
Types of silicone and master model
Of course, when buying material for the manufacture of molds, it is first of all necessary to pay attention to its technical characteristics. Today, only two main types of silicone are available: lubricating and casting.
And for that, and for other material in the manufacture of molds, master models can be used both from metal and wood, and from plastic, cardboard or even just paper.
This variety is very good for making molds. This is a very viscous silicone, applied to the master model with a special brush. An example of such a material is the ABRO heat-resistant auto-sealer
It is also a good material for making molds. When using it, the master model is installed in the flask and filled from above. It consists of a liquid silicone for the forms of this variety of two components: a hardener and a base. Before pouring, they are thoroughly mixed, and then placed in a vacuum chamber to remove air bubbles. A very popular material of this type is, for example, "Pentelast-708S".
The coefficient of elongation
What characteristics can be considered the most important when choosing a material such as liquid silicone? For the manufacture of forms, in principle, fit almost any of its varieties. However, pay attention to some indicators when buying still worth it. The most important parameter characterizing the quality of silicone is the coefficient of elongation. In modern materials, this figure varies within the range of about 200-1300%. The larger this number, the stronger the hardened silicone can stretch, and the more the number of castings withstands the mold made of it.
In practice, usually 700-800 percent one- or two-component liquid silicone is used. For the production of molds, it usually fits perfectly. Products made from a material with such an elongation factor can easily withstand up to 80 castings. This indicator can be smaller or larger, depending on the complexity of the configuration of the master model.
Viscosity of silicone
This is also an important indicator, which has a huge impact on the quality of the finished form. Liquid filling silicone for molds has a very low viscosity. In the process of work, it easily fills the smallest depressions of the master model. And therefore it is advisable to use it for the manufacture of forms of a very complex configuration.
The viscosity in the CPS is measured. In 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 elongation, when selecting silicone, attention should be paid to:
Work time. The higher this value, the longer the material retains its viscosity.
The polymerization time. This characteristic is also important enough. It shows, for what time interval the filled form collects the declared coefficient of elongation.
Two-component liquid silicone for mold production usually hardens and polymerizes longer than viscous. This can be attributed to the advantages of the material. After all, when working with him, the master does not need to hurry anywhere.
How to apply
Use liquid silicone to make molds as follows.
The master-model is fixed on the stand with the aid of a droplet of super-glue and is coated with a special separation compound. At home, it can be, for example, petroleum jelly or engine 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.
Vacuum compound is poured into the flask with a thin trickle. This is necessary in order to get as little air as possible into the liquid material.
The opaque is placed in a vacuum unit for 1-2 minutes. Re-treatment is necessary in order to remove from the silicone absolutely all the air that got into it when pouring.
The mold is frozen for about 5-6 hours. The final polymerization takes place in a day or three. At the final stage, the mold is removed from the flask and cut in half. After that, the master-model is taken out of it.
Forms of viscous silicone
In this case, a slightly different technology is used. Opoku in the manufacture of a mold of silicone is not used. The master model is simply coated with the 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 simplicity of making molds. He deserved great popularity, including for his low cost. The price for a quality silicone can fluctuate only in the range of 450-750 rubles.
In specialized stores or on the Internet, you should look for silicone, designed specifically for making molds. The matter is that today the most various kinds of this material are issued. For example, sold silicone liquid fishing. It is used to lubricate braided yarns on tackles, which prolongs their service life and increases the casting range. For the manufacture of forms such a silicone, of course, is not suitable.
How to make in home conditions
In order to make liquid silicone for molds with your own hands, you need to buy ethyl alcohol and liquid glass. Also need a plastic bottle and a wooden stick. Since the components of silicone are quite caustic materials, thick rubber gloves should be worn on the hands. The procedure for manufacturing is as follows:
Liquid glass and ethyl alcohol are poured into the plastic bottle in equal parts.
The mixture is thoroughly mixed with a wooden stick.
After it thickens, it needs to be taken out of the bottle and carefully stretched with your hands.
Silicone, cooked in this way, resembles a plastic sticky rubber and from it you can make any shape.
Silicone molds for oven
Of course, for the manufacture of such castings, environmentally unsafe materials can not be used. In this case, liquid silicone for molds is made a little differently:
Three tablespoons of potato starch are covered in a glass of yoghurt.
Pour there the same silicone sealant in the same amount.
Stir everything for ten minutes.
Of the so prepared silicone, you can easily mold a simple baking dish. Before pouring the dough, it must be greased with vegetable oil.
Use of silicone molds
So, liquid silicone is often used to make molds. The use of products molded from the "starch" material, allows you to bake the original cakes, cakes, etc. And how are the forms made of conventional silicone used? Most often they are used for the manufacture of beautiful products from all sorts of two-component fillings. Any large objects using silicone molds are usually not manufactured. Therefore, for the mixing of the components of fillings at home, conventional medical syringes are used. Then they are tinted with a drop of dye and poured into the mold through a spaced-apart casting hole.