What is a plastic mold

Making silicone molds - step by step instructions for silicone molds


In order to be able to make beautiful castings or jewelry with epoxy resin, it is essential to use a good negative mold. These are commercially available in numerous designs. However, if you want to dare to create special, individual shapes or just want to build something yourself, then you can make a silicone mold yourself without much effort. We'll show you how to do this in this post.




Working with epoxy resin

To work with Epoxy resin the resin and a corresponding hardener are the basic requirements. Depending on which project you want to dedicate yourself to, there are also other materials such as different color pigments. Polished silicone molds are also often required. There are practically no limits to creativity when it comes to shaping: cubes, balls, pyramids, stars, hearts, flowers, coasters and all kinds of figures of all kinds. Everything is possible and can be filled with epoxy resin, for example, to create beautiful works of art or gifts.

You put the finished epoxy resin mixture in the shape of your choice. Either we use the mixture as clear as glass or color it with liquid paints or pigments. Then, if you want, you can add various elements such as glitter, stones, shells, flowers, etc. After hardening, carefully remove your finished work from the mold.




Silicone molds available on the market

The fact that it acts like a release agent makes silicone ideal as a material for casting molds. The finished resin objects can be easily removed from the mold after curing thanks to the flexibility of the silicone. Another advantage results from the fact that silicone is considered non-toxic. The fact that it is used as a common material in baking molds or even pacifiers shows that this material is completely harmless. In addition, almost no allergies to silicone are known to date. There is already a very large selection of ready-to-use silicone molds on the market. Especially beginners in this technique can use silicone baking molds or polished silicone molds specially made for working with resin.

If you are interested in ready-to-use silicone molds for epoxy resin casting, here are our recommendations:


However, a disadvantage of many of these silicone molds (especially baking molds) is that the stress on the material is extremely high when working with epoxy resin. The first signs of wear and tear, such as a dull surface, quickly appear. As a result, the resin becomes more and more difficult to remove from the mold. In addition, as already mentioned, many shapes are available. Nevertheless, these are of course given and limit your own creativity if necessary. The solution: You can easily make your own silicone mold!



It depends on the degree of hardness

The basic material for making silicone molds is Silicone rubber. You can get this from specialist retailers. Silicone rubber is a soft mass that hardens very quickly and is then extremely elastic. Nevertheless, silicone is not infinitely flexible: If the material is overstretched, breaks or cracks can easily occur. The degree of hardness determines the brittleness of the material. In the trade you get Silicone rubber in different degrees of hardness. The degree of hardness of the silicone is given in Shore. The following rule of thumb applies here: the lower the Shore value, the higher the elasticity.

  • Shore 0 to 20: Soft material with a very high flexibility. However, this material is also relatively unstable.
  • Shore 20 to 40: Fairly dimensionally stable material with medium elasticity.
  • Shore 40 to 80: The material is quite hard and has hardly any elasticity. It is very dimensionally stable, but on the other hand also easily brittle.

Which degree of hardness you should choose for your project depends on what you want to use the silicone for. In addition, working with one degree of hardness may be easier for you than with another. The only way to do this is to try it out. Basically, it can be said that soft silicone naturally has the advantage that you can easily remove your finished workpiece from the mold after it has hardened. However, if the degree of hardness is low, the shape is also very unstable and deforms relatively quickly. In this regard, silicone casting molds with a higher Shore value are of course more difficult to handle, since the casting cannot be easily removed. In addition, care must be taken that they do not break or tear when triggered. With careful handling, however, they can be used very often because of their high dimensional stability. Because they practically do not deform at all.

In addition to the degree of hardness, the viscosity of the silicone also plays a role in the selection. Depending on the project, you can opt for thick or thin silicone rubber.

If you want to make chocolate or baking molds with the silicone, you have to pay attention to the food safety and heat resistance of the material used. Heat resistance up to 200 ° C should be given. If you want to work with epoxy resin, concrete or other chemical casting materials, you should make sure in advance that the silicone you are using is resistant to chemicals. If you are not sure whether your silicone meets your requirements, read the manufacturer's data sheet or seek advice from specialist retailers. If you want to make a silicone mold yourself, you have the choice between two variants: a negative mold with an original form or a negative form without an original form. We would like to go into the differences between these two variants in more detail below.



Negative forms With Manufacture the original form

The negative form with the original form is perfect for making a duplicate. For such a project you need a framework. After the silicone has been poured in, this ensures that it does not spread out in an uncontrolled manner. If you want to build the frame yourself, then use the dimensions of the object you want to reproduce as a guide when building it. Since silicone is quite expensive, this procedure makes sense in order not to use up a lot of the material unnecessarily. Your self-built frame must be absolutely tight in any case. This is the only way to ensure that the material does not unintentionally flow out into any cracks or under the edges when pouring silicone. Instead of a frame, you can also use empty plastic packaging to pour the resin.

Now you can put the blank in the frame and prepare the silicone. As always, you should carefully follow the manufacturer's instructions. Then the mass is evenly distributed in the frame and allowed to harden. After that, the shape can simply be removed from the frame.



Negative forms without Manufacture the original form

To make the silicone malleable for this type of processing, put the mass in a bowl that contains a mixture of water and washing-up liquid. Then the prepared blank is enclosed with the now flexible silicone. Make sure you use enough mass. If you are too economical with the silicone at this point, your shape will later become brittle and unstable.

If you want to make a silicone mold in this way, don't forget that the mold must have an opening at the end through which the object can be removed. Alternatively, the shape can also be cut open at one point after it has hardened.

Images: Van Rossen / JLORTIZ / shutterstock.com



Some considerations before silicone pouring

Before you start pouring the mold, there are a few things you should do to think about your project. For example, the choice of the right silicone mass depends on the nature of the blank. You should make the following considerations in advance:

  • How is the surface of the blank designed? Is it very smooth or does it have grooves, edges or ornaments, for example? This is important in order to decide on the optimum degree of hardness for the silicone. If the surface of the blank is irregular, you should use a soft silicone, so that the resin cast can later be removed from the mold as well as possible. A silicone with a higher degree of hardness also works with a simpler blank.
  • How big and heavy is the blank? What material should the form be poured with later? These considerations are also important for choosing the right degree of hardness. If you hastily decided on a soft material, problems with the stability when pouring the mold later are quite possible.

In order to be able to make silicone molds yourself, it does not necessarily have to be the expensive special silicone. The use of bathroom silicone, which is significantly cheaper to buy, is also possible here. This inexpensive alternative is particularly useful for beginners. This way you don't get annoyed about unsuccessful, expensive attempts. When using bathroom silicone, however, you should note that you can only make simple silicone molds with it. You won't get filigree, detailed images with this.



You need this material for the production of silicone molds

If you want to make a silicone mold yourself, the nature of your project will determine the exact material requirements. In the following list, we assume a negative form with an original form:

It is extremely important that very little, or even better, no silicone runs out of the frame when pouring. Therefore all joints are closed with the modeling clay with the help of the toothpick or cotton swab and the frame is sealed as well as possible.



Making a silicone mold - step by step instructions

At first glance, it might sound very difficult to make silicone molds. With our step-by-step instructions, however, it will not be a problem for you as a beginner to make a successful negative form.


Construction of the frame

  • The frame into which the silicone is to be poured must be sealed as well as possible so that no material later leaks out through any cracks. In addition, the frame must completely enclose the blank.
  • The base plate of the original form should be smooth. All smooth materials except glass are suitable for this. This would not repel the silicone and so later triggering without damaging the silicone would be practically impossible. It makes most sense to use a smooth one MDF board. Smoothly planed wood is also very suitable for the four side walls that enclose the base plate. Now glue the sides with the help of a Hot glue gun on the base plate. These side walls should protrude about ten millimeters above your blank. You should thoroughly clean the joints in the form modeling clay seal. They are suitable for smoothing the mass Cotton swabs or toothpicks.
  • When the frame is ready, you place the blank in it. The side that is to be displayed must face up. The object can be attached to the base plate with a bit of double-sided adhesive tape or a drop of hot glue, for example. Fix the blank well enough so that it cannot slip when you fill in the silicone mass.


Mixing the silicone

  • After you have weighed the required amount of silicone, mix the two components in a 1: 1 ratio. You use one to mix Mixing cup and one Wooden spatula. Be careful not to do too much silicone to waste. For this you can either calculate the volume or determine the approximate need with the help of a measuring stick.
  • It has proven useful to mix several small portions instead of one large portion of silicone. These can be mixed together more easily without clumping. Since silicone is very tough, it is almost impossible to stir a very large amount of it. So it's better to divide up the silicone by using several small cups.
  • To dissolve the air bubbles in the mass, you can tap the bottom of the mug on the table top a few times after mixing. Before you pour the silicone into the frame, you should wait a few minutes. This is the only way that any air has really escaped from the crowd.


Pour in silicone

  • If you have decided on wood as the material for the construction of the frame, then this must be thoroughly included before pouring the silicone Release agent be sprayed. Alternatively, you can also coat the frame with oil. But be careful: Not all oils are compatible with silicone and may attack the surface of the material. Therefore, you should pay attention to the manufacturer's information in advance.
  • Now the Silicone mass be poured over the blank into the frame.
  • Pouring the silicone is pretty easy on a large object with a smooth surface. The liquid silicone is poured slowly over the blank from a relatively great height. Make sure that it is completely enclosed in the mass.
  • In the case of a blank that has many edges, corners, angles or cracks, these must be poured first. This works best with a very thin silicone jet. Then you can use the rest of the silicone to frame it. This procedure guarantees that all details are visible in the subsequent illustration.
  • The frame is then filled with the remaining mass until it protrudes over the object by approx. Five millimeters.
  • Finally, the air bubbles should be removed from the poured silicone. To do this, carefully tap all four sides of the frame so that the air can escape. Then you can let your shape harden.


Remove the finished silicone mold

  • The curing time of the silicone mold depends on the silicone used and its size. It can vary between one and 24 hours. If you want to check that the silicone is fully cured, you can gently press into the mold with your finger. If you notice that the mass has hardened, the silicone mold is now released from the frame. If this has been treated thoroughly with mold release agent or oil beforehand, this usually works without any problems. For the final straightening of the edge, it is best to use one Scissors, a box knife, or a scalpel.
  • To keep the silicone supple and to maintain it, you can take it with you after it has been released from the frame and after each use Talcum powder rub in.




Make a two-part silicone mold

Two-part molds are of course ideal for resin casting. When working with epoxy resin, impressive, three-dimensional objects can be designed in which a wide variety of materials such as stones, flowers or other objects can be poured. But two-part molds are of course also very interesting for model builders, as they can be used to produce a wide variety of objects. With two-part silicone molds, parts of different sizes and different materials can be easily combined. Materials such as concrete or plaster can be used to create house facades, gates or bridge pillars, which can be beautifully painted and decorated after hardening

In addition to the materials already listed above for a simple shape, you also need some modeling clay for two-part shapes. With this you fill up the frame halfway. The surface must then be smoothed and the corners well lined. Now half of the blank is pressed into the clay and the silicone is filled into the frame. After hardening, the putty and the silicone mold are removed. The finished silicone mold is placed directly back into the frame. Then the blank is placed into the previously prepared recess. In order to be able to separate the mold halves later, you have to coat the mold with Vaseline before you pour liquid silicone into the frame again. This silicone mass must also harden well.




Silicone molds with undercuts

Silicone molds with so-called undercuts can be a particular challenge. Blanks with undercuts have clearly visible, protruding corners and edges that can get in the way when they are removed from the mold. If these undercuts are relatively small and you are using soft silicone (Shore 0 to 20), then these edges should not cause any major problems. It gets a little more tricky with larger undercuts. In this case it is advisable to make a two-part or even multi-part mold. You should definitely opt for the flexible, soft silicone rubber and be meticulous when removing the object that it is not overstretched.

If it is not possible to remove the blank in the normal way, you can cut open one edge of the silicone mold and then remove the blank. You can then close the resulting cut by attaching some very tight rubbers to the mold. It is also very easy to later remove the cast workpiece from the negative mold.



Valuable tips and tricks

  • If it is too time-consuming for you to build a frame out of wood in advance, then there is a very simple alternative. Take a base plate made of smoothly planed wood and then put a frame made of Lego blocks which you glue on the plate. This gives you absolute flexibility in terms of size and shape when designing. When sealing and later pouring the silicone, you proceed in the same way as with a wooden frame.
  • The optimum room temperature for drying silicone is between 18 ° and 22 ° C. If the temperature is higher, the material can clump together because it dries too quickly. If the room temperature is lower than 18 ° C., the drying process will be unnecessarily prolonged.
  • Another little trick if you are unsure how much silicone you actually need: Build the wooden frame as described and fix your blank to the base plate. Now you fill the mold with rice until it protrudes about one centimeter over the object. Since the weight of the rice roughly corresponds to the amount of silicone required, all you have to do now is weigh it.
  • An important tip at the end: In order not to lose the joy of your project right from the start, first plan a relatively simple form and take your time to implement it. Gradually you can then increase the level of difficulty.



Inspirations for DIY silicone molds

Even if you don't have a lot of experience in making silicone molds, you can still dare to work on small pieces of jewelry. There are no limits to your creativity. Pendants in various shapes made from epoxy resin and embedded materials are real eye-catchers. If your child is fascinated by your favorite piece of jewelry, which may be valuable, you can create a wonderful duplicate for him with sparkling extras such as incorporated glitter particles.

If you are already a little more experienced in casting molds, take on the challenge of a self-cast chess set made of epoxy resin. A unique gift idea for chess fans, where the effort will definitely pay off in the end. Common silicone molds are easily available in stores. However, do you want yourself let off steam creatively and create a truly unique piece, you can't avoid making a DIY silicone mold. Just give it a try - hardly anything can go wrong with our instructions 🙂