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Guide: copying a wooden ornament
Copying a wooden ornament
With this guide you make an exact copy of a wooden ornament. You create a silicone mould with an acrylic resin support shell and then cast a strong acrylic resin final model. The example is a 15th-century wood carving.
📄 Download this guide as PDFWhat are you going to make?
You make a durable, exact replica of a wooden ornament. First you mould the original in a two-layer silicone mould, which you reinforce with an acrylic resin support shell. Then you cast an acrylic resin final model in that mould and reinforce it with fibreglass.
The original
A 15th-century wood carving. The beeswax has been removed and the wood sanded; what remains is a very dry, splintered and porous surface.
The ornament from above, clearly showing the depth of the carving.
💡 Suitable for advanced users. Work precisely and mind the pot life (working time) of both the silicone and the acrylic resin.
Required materials
🛒 From the webshop
🧰 Supply yourself
- Scale
- Mixing container and stir stick or mixer
- Drill with mixing attachment (for the acrylic resin)
- Cloth or sponge
- Bucket
- Wooden slats (for drying)
Product specifications
| Property | Value |
|---|---|
| Silicone mixing ratio | C-20 A : B = 100 : 2 (2% B) |
| Silicone thickener | 1% Thixo C in the second layer |
| Silicone layer thickness | around 0.5 cm |
| Silicone curing | around 24 hours |
| Acrylic resin thickener | 1% Thix A (support shell) |
| Acrylic resin working time | around 15 minutes |
| Release agent | Release paste on the wood |
Preparation
Before you coat the ornament, good preparation matters: the mould will capture every detail later. Remove dirt, dust and unwanted irregularities and bring the ornament into the desired state. Fill cracks, fill holes and repair or replace any damage.
Blow away dust and loose particles, for example with compressed air, so the surface is completely clean.
⚠️ Many materials have a pot life (working time). Lay everything out before you start so you can work quickly. Wear latex gloves.
Assess and repair the ornament
Assess the ornament and repair damage and unwanted irregularities. With this porous 15th-century wood carving, careful preparation is especially important.
Remove dust
Blow away dust and loose wood particles with compressed air. A clean, dust-free surface gives a sharp, detail-accurate mould.
Apply release paste with a cloth
With wooden models, no adhesion between the silicone and the wood may occur, and hardly any oil from the silicone may seep into the wood. That is why we first apply a release paste. The liquids evaporate from the paste and a releasing residue remains.
Apply the paste to the wooden surface as described. Use a cloth or sponge for the flat areas.
Apply release paste with a brush
Treat hard-to-reach and deep-lying areas with a brush so the entire surface gets an even layer of release paste.
Let the paste dry to a white, powdery residue. This residue protects the wood and is easy to remove later with water.
💡 A good release layer is crucial on porous, dry wood. Never skip this step.
Pour the first silicone layer (without thickener)
Pour a quantity of Silicone C-20 A into the mixing container and add 2% Silicone C-20 B. Mix the components well with a spatula.
Pour the silicone onto the ornament in a thin stream and fill all deep and hard-to-reach areas. This first, thin layer captures the finest details.
Apply the second silicone layer (with Thixo C)
The second layer is the support layer: it builds the mould up to thickness and gives rigidity. Pour Silicone C-20 A into the container again and add 2% C-20 B. Mix well.
Now add 1% Thixo C and stir again thoroughly. Let the mixture rest for 2 minutes so the thickener can do its work.
Apply the thickened silicone with a brush or spatula. Do not trap air; treat detailed or deep areas by dabbing. Apply a layer about 0.5 cm thick.
⚠️ Ensure a releasable shape: make all forms tapered so the support shell can later be lifted off straight. For example, completely fill deep areas beside the head so no trapping undercuts form.
Smooth the silicone
Smooth the top layer as evenly as possible with a spatula or brush. A soapy solution helps: dip your hands (with latex gloves) into it, then the silicone sticks less and you can smooth by hand.
Let everything rest for a day so the silicone fully cures.
Cut the triaxial fibreglass cloth
The silicone is fully cured after 24 hours. Now we make a support shell that holds the silicone mould in shape during casting.
Cut the triaxial fibreglass cloth into manageable strips that fit the model, for example strips 1 metre long and 20 cm wide, plus several pieces of 20 by 20 cm.
Mix acrylic resin for the support shell
Fill a roomy bucket with the calculated amount of Acrylic resin A component (liquid). Add the correct amount of Acrylic resin B component (powder) and start mixing immediately, preferably with a drill and mixing attachment, until you get an even mass without lumps.
Then add 1% Acrylic resin thickener Thix A (so 150 grams for a 15 kg mixture). Apply the acrylic resin around 5 mm thick over the entire silicone model.
⚠️ Acrylic resin has a working time of around 15 minutes. Work with amounts you can process within that time.
Lay in the first layer of fibreglass cloth
Lay the triaxial fibreglass strips onto the still-wet acrylic resin and press them on gently. The acrylic resin must not yet begin to cure.
Use a wide brush to press the cloth down well and spread the acrylic resin evenly. Smooth the surface and apply a second and possibly third layer the same way. Then let the support shell dry for 24 hours.
Assemble the mould in the support shell
Once the support shell has cured, remove it from the silicone. Then carefully remove the silicone mould from the original ornament.
Place the silicone back into the support shell correctly without deforming it. Set everything level and fix the mould so it cannot shift or tip over.
Cast the acrylic resin final model
In a large bucket, mix the desired amount of acrylic resin as in step 7, but now without thickener: the resin must be poured as fluid as possible.
Pour at one spot and let the resin flow into the mould calmly, without splashing. This leaves few air bubbles. After pouring, tap against the mould so remaining air bubbles release and rise. Let the acrylic resin set for around 30 minutes.
Reinforce the final model with fibreglass
Mix a small amount of acrylic resin (around 1 to 2 kg) and spread it over the cast model. Apply fibreglass cloth and smooth it with a brush or by hand.
Repeat this 3 to 5 times for sufficient strength. Then let the model cure in the mould for 24 hours. Remove the model after 24 hours and let it cure and dehumidify for another 24 hours, on wooden slats if needed.
Final result
On the left the silicone mould with acrylic resin support shell, on the right the cast acrylic resin copy. An exact, durable replica of the original wood carving.
Before
Before: the original, dry and porous wood carving.
Before and after
After: the finished acrylic resin copy with all the details of the original.
Special instructions
- A good release paste is essential on porous wood to prevent adhesion and oil seepage.
- Make all shapes tapered (releasable) so the support shell can lift off the mould straight without trapping.
- Process acrylic resin within the working time of around 15 minutes; otherwise work in smaller portions.
- The white powdery residue of the release paste is easy to remove with water after demoulding.
- Wear latex gloves and ensure good ventilation.
Storage
Uncured components
Store the silicone components, acrylic resin and thickeners well sealed, dry and at room temperature. This preserves their processing properties.
Cured mould
Store the silicone mould inside the support shell, level and free of pressure, so the mould keeps its shape and stays reusable for multiple casts.
Frequently asked questions
Why a release paste and not a liquid release agent?
On porous wood, liquid release agent penetrates too deeply. After drying, the paste leaves a releasing residue that protects the wood and is easy to remove with water.
Why two silicone layers?
The first thin layer without thickener captures the finest details. The second, thickened with Thixo C, builds the mould up to thickness and gives rigidity.
What is the acrylic resin support shell for?
The support shell holds the flexible silicone mould in shape during casting. Without it, the mould would deform and the copy would not be dimensionally accurate.
Why must the shapes be tapered?
Tapered, releasable shapes ensure the support shell can lift off the mould straight without undercuts that trap or damage.