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How to make a decorative panel from concrete (GFRC)

This tutorial shows the process of making a decorative fiberglass reinforced concrete (GFRC) panel using various Schouten cast rubbers and casting materials.

Step 1: make an original pattern

The pattern was made from wood. Eventually this small pattern will be repeated to form a larger panel.

Step 2: make a mold of the original pattern

The Eurosil 22 silicone mold (not shown) is made from the original wooden model. The wooden model is first treated with pore sealant (let it set for 15 minutes), after which Pol-Ease 2500 release agent will be sprayed on the model so that the silicone rubber will dissolve easily.

Step 3: Make a “plastic” copy of the model to edit the product.

EasyFlo 60 Liquid Plastic is used to make a copy. It is a good way for a quick replication of the model. EasyFlo 60 has a 2 to 2.5 minute pot life, easy to mix with 1A:1B mix ratio by volume, and a 15 to 30 minute low viscosity demoulding time. This plastic can be poured into silicone molds without any release agent.

The plastic model is treated with different materials (eg Bondo, primer) until a final design is reached. If primer is being applied to the pattern, make sure it is completely dry before moving on to the next step. The results can be accurately copied up to 2 microns (Eurosil silicone).

Step 4: make a mold of the final model

A PlatSil® 73-25 or Eurosil 22 silicone rubber mold must be made from the last model made. PlatSil 73-25 / Eurosil is a soft, platinum silicone rubber with a 1A:1B mixing ratio. This silicone has a 15-minute pour time and a mold release time of 4-5 hours.

Step 5: Make a bigger pattern

When the mold is produced, several EasyFlo 60 copies are cast and assembled into a larger pattern of the models. The pattern is adhered to a base plate with edges built as walls around it, the edges are sealed with plasticine clay (water free) where necessary to prevent leakage. The base plate and the edges are made of melamine laminated chipboard.

For this pattern, we make sure to create a mold with walls that are the least +/- 1.5cm (1/2″ thick) to mold

A polyurethane rubber mold is made of the new model, the Pol-Ease 2300 release agent is applied to the model, the edges and the base plate are then brushed out for better releases.

For this pattern, we make sure to create a mold with walls that are the least +/- 1.5cm (1/2″ thick) to mold.

Release agent does not need to be applied when casting silicone molds when we are casting polyurethane resin and resins. However, when casting polyurethane resins and resins in polyurethane rubber mold, release agent MUST be applied. The release agent can be a nuisance for some products and cases.

Polyurethane rubber is cheaper than silicone rubber.

Step 6: make a mold of the new model

Poly 74-30/74-40 or 75-60/80 (for the larger patterns) is a medium soft polyurethane rubber and can be used to make the new mould. For example, FormRub 35 has a 1A:1B mixing ratio, 15 minutes pot life and 16 hours to be unloaded.

Poly 74 /75 series rubbers are specially designed for pouring heavy elements such as pouring cement or concrete. Poly 74 / 75 series is weighed, mixed and poured over the EasyFlo 60 model.

Poly 74 /75 series rubbers are specially designed for pouring heavy elements such as pouring cement or concrete. Poly 74 / 75 series is weighed, mixed and poured over the EasyFlo 60 model.

The mold is unloaded 16 hours later. The edges of the mold are loosened before the entire mold is unloaded.

Step 7: Pour and Assemble the Plastic Copies for a Larger Pattern (if desired)

When the Poly 74 series mold is cast, multiple EasyFlo 60 units are cast and then bonded together on a base plate to form the final large pattern panel.

Plasticine clay is used to seal small gaps between the individual elements as well as to seal the mold box of walls and base plate around the entire pattern and mold.

Pol-Ease 2300 release agent is applied to the model, base plate mold walls and plastiline and then brushed for even coverage of the release agent.

Step 8: Make the final mold for pouring the concrete.

Poly 74-20 / 74-30 / 74-40 Liquid Rubber is used to make the final mold for pouring concrete. Poly 74-20 where a Poly 74-30 and Poly 74-40 are the softer polyurethane casting rubbers and do not require a release agent in all cases when pouring concrete. The softer the rubber the better it is for intricate or complex patterns of the models.

Poly 74-20 has a 1A:2B mix ratio, a low viscosity of 800 cP, a 30 minute pour time and a 16 hour mold release time. the 74-30 has a 1A:1B mix ratio, a 30 minute pour time and a 16 hour demoulding time, and a viscosity of 8000cP.

The cured model after 16 hours.

Since the plastic model was not damaged during the mold making process, it can be reused for more molds.

Step 8: Pouring (GFRC) Concrete

A GFRC mix must be manually poured and processed to have an even distribution of the concrete with the desired detailing (treatment varies depending on the product).

Before removing the concrete from the mold, the entire mold is first carefully turned over. All edges must be loosened after which the entire mold can be slowly released from the concrete.

The concrete can then be sanded, blasted, stained and sealed if desired.

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