Moulds
1.0 A1 is excellent for casting in moulds and produces exact copies of the original. You can use moulds made of various materials, such as silicone rubber, concrete forming plywood, PU and polyester.
It is important that the A1 cannot stick to the mould. Silicone rubbers are very well suited for this, which is why we recommend working with silicone rubber moulds.
A silicone mould has several other advantages, such as:
- The flexibility of the mould is very useful when demoulding the A1 object.
- Because A1 does not shrink but expands slightly during the reaction between the A1 Liquid and the A1 Powder, it creates an exact, detailed impression of the silicone mould.
- A1 does not affect the silicone. This makes it possible to make an unlimited number of A1 casts.
A silicone mould may be less suitable for products that need to be dimensionally stable. In addition, poor-quality (often cheap) silicones with a high oil content can release oil, which is sometimes visible on the A1 object.
Moulds made of sheet material, such as epoxy plywood forms or polyester moulds, work well in practice if they are treated with a suitable release agent. During hardening, A1 expands slightly. This can cause A1 to get stuck in the mould, especially if the mould does not release easily on its own.
Moulds made of gypsum or other porous materials are not recommended, unless they have a fully sealing coating or wax system that prevents moisture from the A1 from penetrating the mould. Otherwise, there is a risk of a (strong) bond between the mould and the A1, and the A1 may weaken.
When using a release agent, some of it may remain on the A1 object after demoulding. These release agents are often based on grease or oil. This can affect the adhesion of finishing coats such as A1 Sealer PLUS, paint systems or an extra layer of A1.
Therefore, we advise using as little release agent as possible, or working with mould materials that do not bond with A1.
2.0 Wax system.
We recommend using a high-temperature wax system as a release agent for your moulds, as we have found that this gives the best results. Silicone moulds normally do not need a release agent.
laminating in a mould
Using a mould in combination with A1 Triaxial Fibre lets you make strong and lightweight A1 objects.
3.0 A1 top layer
When we start laminating, we begin by applying a first layer of A1. This layer can be thickened with Thix A and is often mixed with pigment, sand, metal powder and/or other materials to achieve the desired appearance. Before laminating, it is important to let this layer dry (maximum 1 hour) to prevent the A1 Triaxial Fibre from showing through.
After applying the top (first) layer in a mould, it is time to apply the next (glass fabric reinforced) layers of A1, when the top layer is drying but still feels slightly moist. This moment comes right after the set time of A1 has expired, and it also depends on the ambient temperature, humidity and the use of A1 additives. This way, you get good adhesion between the layers.
Cut the A1 Triaxial Fibre to size in advance and mix a new batch of A1. Apply the unthickened A1 to the A1 top layer. Now you can laminate the A1 Triaxial Fibre into it. Brush from the inside outwards to prevent folds. No drying time is needed between multiple layers of A1 Triaxial Fibre.
If the underlying A1 layer has already cured, first apply a thin new layer of A1, then laminate the A1 Triaxial Fibre into it (wet-on-wet).
Demoulding is often possible after 1 hour. For fragile objects, this may take longer.
4.0 Temperature and humidity
Temperature and humidity affect the set time and curing of A1. For larger objects, A1 Retarder can be used to extend the set time, so you have more time to work on the A1 object calmly. As long as the processing temperature is not too high and the humidity is not too low, this is a good way of working.
We advise against using A1 Retarder for the top layer (gelcoat layer), especially when working in moulds, in hot weather (above 25 to 30°C) combined with low humidity. In hot, dry weather, a dry skin quickly forms on the surface, even before curing starts. The curing process seems to have started, but the layer underneath is still soft. This creates a high risk of craquelure in the top layer and poor curing. The adhesion to other A1 layers will also be weaker. If possible, avoid working above 25°C. Alternatively, you can add A1 Accelerator to shorten the set time of A1.
5.0 Laminating vertical parts
When applying A1 to vertical parts, it can help to thicken the A1 slightly with our A1 Thix A. This increases the viscosity of the A1 and makes it easier to apply a thicker layer of A1 to the vertical parts of the mould.
When applying A1 together with our glass fabric, you do not need to thicken the A1, as the glass fabric helps hold it in place.
DIFFERENT MATERIALS CAN BE USED FOR MOULD MAKING
6.0 We recommend moulds made of silicone
The advantage is that no release agent is needed, as A1 and silicone do not stick to each other. Because silicone is flexible, the A1 object can be released from the mould even when the shape is complex.
A1 does not affect the silicone, so you can produce many A1 objects from a single mould.
7.0 EPS foam
EPS foam is very easy to shape, which makes it an excellent mould material. You can use the EPS as a positive mould and apply the A1 directly over the shaped EPS.
However, when using EPS as a negative mould, you first need to apply a layer of A1 over the EPS to cover all the holes. Next, we recommend applying a coating or paint system over the A1, followed by a release agent. The EPS mould is then ready to use.
This method works best for one-offs.
8.0 Plywood
Plywood is very effective when smooth, rectangular forms are needed. An additional advantage is the low cost of plywood compared to other materials.
A release agent is necessary to prevent the A1 from sticking to the plywood.
9.0 CNC-milled moulds
A CNC-milled mould, often made of a composite paste, is used for objects that need exact dimensions and often have complex shapes.
An advantage of CNC-milled moulds is that the whole development process can be done on a computer.
10.0 Polyester moulds
Polyester moulds are often used by companies that already have experience in the composite industry. They are very effective because of their dimensional stability.
When producing fibreglass parts in fibreglass moulds, the fibreglass shrinks slightly, which makes demoulding easier.
When using A1 in fibreglass moulds, demoulding needs to be easy, because A1 expands slightly while curing. This creates a risk of the product getting stuck in the mould.
Our advice is to always use a 2- or 3-piece mould, depending on the design, for easier release. You can see an example on page 20 of our design guide. Both ends of the mould can be removed.
The best release agent is a hard wax, preferably a high-temperature one, as commonly used in the FRP industry, such as Honey Plus Wax, TR104 or Mirror Glaze 87.
Apply the wax 2 or 3 times when starting with a new mould. Wipe it on and wipe it off. After that, we advise applying a new layer of wax after every demoulding.
When applied correctly, the wax will not leave marks on the A1 product. However, before painting or applying a sealer, it is best to degrease the surface with Scotch-Brite or an ammonia solution in water. Never use a solvent such as thinner or acetone.
After a few demouldings, you will see that the mould becomes matt (with glossy moulds), and there may be some wax build-up. If there is too much wax build-up, clean the mould and apply new wax.
11.0 3D printed moulds
3D printed moulds are the latest development in mould making. After 3D printing, the mould is CNC milled and sanded to give the desired smooth finish. The mould is then ready for production.
This gives the developer the freedom to use advanced software to develop the required object.
Once all the A1 objects have been made with the 3D printed mould, the mould material can be shredded and reused for a new mould.
12.0 Light spots or colour differences after demoulding
As water evaporates, light spots, colour differences or “water marks” can appear in your product. We suggest demoulding within a few hours after finishing casting or laminating the A1 object. Try to avoid leaving the A1 object in the mould overnight.
13.0 Can A1 be applied to (wet) clay?
A1 can be applied to (wet) clay, but expect the A1 and the clay to interact. This will create a bond between the clay and the A1. After the A1 has cured, you can wash the clay away with water.
Also expect the A1 object to have (lots of) colour spots.
14.0 When releasing the sculpture from a plaster mould, I had to break the mould
A1 adheres very strongly to many materials, and to plaster in particular. That’s why we strongly advise against using plaster or gypsum-like materials as moulds, as the risk of them bonding together is high.
Our customers have told us that a product called shellac might help prevent adhesion between the A1 and the plaster mould. Please test this before using it on your object.
15.0 How do you join A1 parts from a multi-part mould?
In general, you can use A1 as a glue to join the different parts together. With ATP Powder, you can thicken the A1 to fill any gaps between the parts. If you need a very strong connection, we advise using A1 in combination with our glass fabric.
How to prepare your mould to create (almost) invisible joints is beyond the scope of this website, as it is the craft of the mould maker.
