How to Make a Decorative Concrete (GFRC) Panel
This tutorial shows the process of making a decorative glass fiber reinforced concrete (GFRC) panel using various Polytek® mold rubbers and casting materials.
STEP 1: Create an Original Pattern
The following pattern was constructed from wood. Ultimately, this small pattern will be repeated to form a large panel.
![Original Wood Pattern Pattern Making](/content/images/GFRC-Panel_1.jpg)
STEP 2: Make a Mold of the Original Pattern
A PlatSil® 73-25 silicone mold (not pictured) is made of the original wood pattern. Before making the mold, the wood is sealed and Pol-Ease® 2500 Release Agent is applied to the pattern so the silicone rubber will release easily.
STEP 3: Cast a Plastic Copy of the Pattern to Finalize the Design (if necessary)
Oftentimes, pattern makers will make a mold of an original pattern and then cast a copy (or copies) in order to clean-up and finalize the design.
EasyFlo 60 Liquid Plastic, used to make a the copy below, is a great option for fast replication. EasyFlo 60 has a 2 to 2.5-minute pour time, simple 1A:1B mix ratio by volume, and a 15 to 30-minute demold time. This plastic can be poured into silicone molds without any release agent.
![EasyFlo 60 Pattern EasyFlo Copy of Pattern](/content/images/GFRC-Panel_2.jpg)
The plastic pattern is edited with various materials (e.g. bondo, primer paint) until a finalized design is reached.
If primer paint is applied to the pattern, ensure that it is fully dry before moving on to the next
step.
![The Finished Pattern EasyFlo 60 Model Making Plastic](/content/images/GFRC-Panel_3.jpg)
STEP 4: Make a Mold of the Finalized Pattern
A PlatSil® 73-25 Silicone Rubber mold is made of the final pattern. PlatSil 73-25 is a soft, platinum-cured silicone rubber with a 1A:1B mix ratio. This silicone has a 15-minute pour time and a 4 to 5-hour demold time.
![PlatSil® 73-25 Silicone Mold Silicone Mold of Plastic Pattern](/content/images/GFRC-Panel_4.jpg)
STEP 5: Cast Plastic Copies & Assemble a Larger Pattern
When the mold is finished, multiple EasyFlo 60 copies are cast and assembled into a larger pattern. The pattern is adhered to a baseboard, mold box walls are built around it and edges are sealed with plasticine clay where necessary. The baseboard and walls are melamine-laminated particle board.
For this pattern, we make sure to form mold walls that are least 1/2″ thick.
![EasyFlo 60 Pattern Plastic Pattern in Mold Box](/content/images/GFRC-Panel_5.jpg)
A polyurethane rubber mold will be made of this new pattern, so Pol-Ease 2300 Release Agent is applied to the pattern, baseboard and mold box walls and then brushed out.
![Pol-Ease 2300 Release Agent Pol-Ease 2300 Release Agent](/content/images/GFRC-Panel_6.jpg)
![Brush Out Release Agent Apply Release Agent to Plastic Model](/content/images/GFRC-Panel_7.jpg)
You may be wondering why we used a silicone mold for the previous step and are going to use a polyurethane mold for this step. We’re merely doing it to showcase that either option can be used. Two of the main differences between these two options are:
- Release agent does not need to be applied to silicone molds when casting polyurethane resin; however, release agent must be applied to polyurethane molds when casting polyurethane resin. The application of release agent may be a nuisance to some.
- Polyurethane rubber is less expensive than silicone rubber.
STEP 6: Make a Mold of the New Pattern
FormRub 35, a medium-soft polyurethane rubber, is used to make the new mold. FormRub 35 has a 1A:1B mix ratio, 15-minute pour time and 16-hour demold time.
FormRub Series rubbers are specifically designed to stand up to the rigors of concrete casting.
![FormRub 35 Liquid Rubber FormRub 35 Liquid Rubber](/content/images/GFRC-Panel_8.jpg)
FormRub 35 is measured, mixed and poured over the EasyFlo 60 pattern.
![Measure FormRub Liquid Rubber Measure FormRub Liquid Rubber](/content/images/GFRC-Panel_9.jpg)
![Thoroughly Mix FormRub 35 Mix FormRub 35](/content/images/GFRC-Panel_10.jpg)
![Pour Rubber Over Pattern Pour Rubber Over Pattern](/content/images/GFRC-Panel_11.jpg)
For this pattern, we make sure that the bottom of the mold is at least 1/2″ thick.
![Pour Rubber Over Pattern FormRub 35 Mold](/content/images/GFRC-Panel_12.jpg)
The mold is removed 16 hours later. The edges of the mold are loosened before removing the entire
mold.
![Demold FormRub 35 Mold Demold Mold](/content/images/GFRC-Panel_13.jpg)
![Demold FormRub 35 Mold Demold FormRub 35](/content/images/GFRC-Panel_14.jpg)
![The Finished FormRub 35 Mold Finished Rubber Mold](/content/images/GFRC-Panel_15.jpg)
STEP 7: Cast Plastic Copies & Assemble a Larger Pattern (if desired)
When the FormRub 35 mold is complete, multiple EasyFlo 60 copies are cast and then adhered to a baseboard to form the final panel.
Plasticine clay is used to seal small gaps between the individual elements and then mold box walls are constructed around the entire pattern.
![The Final Pattern 20150512_144129](/content/images/GFRC-Panel_16.jpg)
Pol-Ease 2300 Release Agent is applied to the model, baseboard and mold box walls and then brushed out to ensure even
coverage.
STEP 8: Make the Final Mold
Poly 74-20 Liquid Rubber is used to make the final mold for casting concrete. Poly 74-20 is Polytek’s softest polyurethane rubber and often does not require release agent when casting concrete. We have found this rubber to be a good option when working with intricate patterns.
![Poly 74-20 Liquid Rubber Poly 74-20 rubber](/content/images/GFRC-Panel_17.jpg)
Poly 74-20 has a 1A:2B mix ratio, a low viscosity of 800 cP, a 30-minute pour time and a 16-hour demold time.
![Pour Poly 74-20 over Pattern Pour Poly 74-20 over Pattern](/content/images/GFRC-Panel_18.jpg)
![Pour Poly 74-20 over Pattern Pour Mold Rubber over Plastic](/content/images/GFRC-Panel_19.jpg)
![Pour Poly 74-20 over Pattern 74-20 liquid rubber](/content/images/GFRC-Panel_20.jpg)
![Pour Poly 74-20 over Pattern Pour Rubber Over Model](/content/images/GFRC-Panel_21.jpg)
The mold is removed after 16 hours.
![Finished Poly 74-20 Mold Finished Poly 74-20 Mold for Decorative Panel](/content/images/GFRC-Panel_22.jpg)
![Finished Poly 74-20 Rubber Mold (close-up) Poly 74-20 Rubber Mold for Decorative Panel](/content/images/GFRC-Panel_23.jpg)
Because the plastic pattern is not harmed during the mold making process, it can be used to make many more molds, if required.
STEP 9: Cast Concrete
A GFRC mix is manually worked into the details of the mold and allowed to cure (cure times vary depending on the product).
![GFRC Concrete in Poly 74-20 Mold GFRC Concrete in Rubber Mold](/content/images/GFRC-Panel_24.jpg)
![GFRC Concrete in Poly 74-20 Mold Close-up_Concrete in Rubber Mold](/content/images/GFRC-Panel_25.jpg)
The remove the concrete, the entire mold is first carefully flipped over. All of the edges are loosened and then the entire mold is slowly peeled off of the concrete.
![Loosen Edges of Mold Loosen Edges of Mold](/content/images/GFRC-Panel_26.jpg)
![Carefully Peel Back Mold Slowly Peel Off Mold](/content/images/GFRC-Panel_27.jpg)
![Carefully Peel Back Mold Carefully Demold](/content/images/GFRC-Panel_28.jpg)
![Carefully Peel Off Mold Remove Rubber Mold from Concrete](/content/images/GFRC-Panel_29.jpg)
The concrete can then be sanded, colored and sealed as desired.
![GFRC Decorative Panel Decorative Concrete Panel from Rubber Mold](/content/images/GFRC-Panel_30.jpg)
![GFRC Decorative Panel (close up) GFRC Decorative Panel from Rubber Mold](/content/images/GFRC-Panel_31.jpg)
![Decorative GFRC Panel - Standing Up Decorative GFRC Panel](/content/images/GFRC-Panel_32.jpg)