What will you make?

You will create a single-use moulding mould of a body part — usually a hand — using 3D-Gel (alginate). The alginate cures within minutes into a firm, elastic gel that captures every detail of the skin: lines, creases and even fingerprints. You then pour a casting material of your choice into this mould to make an exact 3D copy.

Alginate is completely skin-friendly and is also used in dentistry for impressions. Because the mould is organic and contains water, it is single-use and must be cast within half an hour.

Required materials

Product specifications: 3D-Gel (Alginate)

Preparation

Before you start moulding the body part, it is wise to open the pack of 3D-Gel and lay out all required materials. Alginate cures very quickly, so you will have no time to search for items while working. Keep the scale, mixing cup, water and the container for the hand within easy reach.

Expose the body part and remove any jewellery you do not want to mould (or leave it on, like a wedding ring, if you do want it in the cast). Make sure you can work quickly and without interruption, and practise the pose of the hand beforehand if needed.

Step-by-step guide

Lay out materials and choose a container

Lay out all materials: the pack of 3D-Gel, the scale, a mixing cup, water and the mixer or whisk. Choose a bucket or container that fits the hand comfortably in the right position. With a container that is too small, the hand touches the edge and takes on an unnatural shape. A container that is far too large simply wastes material.

💡 Tip: Choose the container size so that about 2–3 cm of space remains around the hand. This captures every detail without using unnecessary alginate.

Weigh out the powder

Determine how much alginate you need based on the size of the body part and the container. Weigh out the desired amount of 3D-Gel accurately in the mixing cup. For a single adult hand you usually need ± 300 grams of powder.

Add water in the correct ratio

Add the water in a ratio of 1 part 3D-Gel to 4 parts water (by weight). So to 300 grams of powder you add 1200 grams of water. Use cold to lukewarm tap water — with lukewarm water the gel cures slightly faster, with cold water you have a little more time.

💡 Tip: Want more working time? Choose the Slow or Extra Slow variant, or use colder water. Warmer water speeds up curing.

Mix to a smooth paste

Mix the alginate and the water thoroughly until a smooth, lump-free paste forms. Use a mixer, a power drill with a stirrer or, if needed, a whisk. Work quickly but thoroughly.

⏱️ Note: Never mix for too long. The gel starts to cure in less than 1 minute. As soon as the mixture is smooth, move straight on to the next step.

Place the hand in the mixture

Place the hand in the mixture and move the fingers vigorously back and forth so that any air bubbles between the fingers and in hollow spaces can escape. Then bring the hand into the desired final pose.

Now hold the hand completely still in the right position. Any movement after curing causes cracks or loss of detail in the mould.

💡 Tip: Support the wrist or arm with your other hand or a support, so the position is effortless to hold still throughout the curing time.

Demoulding

Feel the gel after 3–5 minutes. If the gel feels like a very stiff pudding, it has cured and you can carefully remove the hand. First move your hand and arm gently so that air enters the cavity and the vacuum is released. Repeat this carefully with the fingers.

⚠️ Note: Although the gel is strong and elastic, it can tear. Never pull with force — first work the air in all around so the hand releases on its own.

Cast the mould

Fill the mould with your casting material of choice: acrylic resin, porcelain plaster, wax or silicone. First fill the mould halfway and turn it gently so that all air escapes from the fingers. Then stand the mould upright again and fill it the rest of the way.

⏱️ Cast within 30 minutes: The mould is organic and contains water. If you wait longer, the alginate releases water and the mould loses detail. So cast immediately after demoulding.

Cure and remove the gel

Let the casting material cure completely according to the working time of the chosen material. Then simply remove the alginate from the model by hand — the gel tears and peels off easily. Dispose of the used alginate with the green waste or on the compost heap.

💡 Tip: After curing, finish the cast with fine sandpaper for a smooth result, or apply a layer of Gilding Wax for a metallic effect.

End result: an exact 3D copy of the hand, cast in the home-made alginate mould

Special notes

• The most common mould is a hand or several hands, but much more is possible: children's hands and feet, faces, a hand with a wedding ring, two shaking hands or even a dog's paw.
• You mould a pregnant woman's belly by applying the alginate with a spatula and adding a support cap, for example of plaster bandage.
• When choosing the casting material, check that it is resistant to the moisture from the alginate. Plaster, acrylic resin, wax, silicone and concrete are suitable.
• The use of polyurethane, polyester and epoxy is strongly discouraged — the moisture from the alginate disrupts the curing of these materials.
• An alginate mould is always single-use. If you want several identical copies, first cast a silicone mould from the first casting.

Storage

Uncured alginate powder

Store the powder in its tightly closed original packaging in a dry place at room temperature. Alginate powder is sensitive to airborne moisture: an open or poorly closed pack will clump and lose its effectiveness. With correct storage the powder keeps for a long time.

Cured alginate mould

A cured alginate mould is not shelf-stable and not reusable. Cast it within 30 minutes and then dispose of the used gel with the green waste or on the compost heap. The material is organic and fully biodegradable.

Frequently asked questions

How much alginate do I need for a hand?

For a single adult hand you usually need about 300 grams of powder with 1200 grams of water. For a child's hand half that is often enough; for two hands or a larger container you need more. Choose the container so that 2–3 cm of space remains around the hand and adjust the amount accordingly.

Why can the mould only be used once?

Alginate is an organic material that consists largely of water. As soon as you remove the hand, the gel starts to release water and dry out, causing it to shrink and lose detail. That is why you cast the mould immediately and use it only once.

Which casting material can I use?

Plaster, acrylic resin, wax, silicone and concrete are all suitable. Avoid polyurethane, polyester and epoxy: the moisture from the alginate disrupts the curing of these materials and gives a failed cast. If you do want to cast in epoxy, first make a silicone mould from a plaster casting.

Is alginate safe for the skin?

Yes. Alginate is skin-friendly and is also used in dentistry to make impressions. It cures without generating heat and releases from the skin on its own, without the need for a release agent.

Can I make several identical copies?

Not directly from the alginate mould, as it is single-use. If you want a series of identical copies, first cast a hard piece in plaster or acrylic resin, then make a reusable silicone mould from it and cast as many copies as you like.