How to waterproof plaster with Aqua Shield: dosage and 3 methods

TL;DR: To waterproof plaster, use Aqua Shield in one of three ways: mixed in instead of water (50 g per 100 g of Aqua Resin), brushed onto the dry piece, or by dipping. Mixing it in protects the piece all the way through; brushing and dipping also work on finished pieces, including traditional plaster.

Introduction

Waterproofing plaster is the step that turns a pretty decoration into an object you can actually use: a vase that holds water, a candle holder that doesn't get stained by wax, a coaster that leaves no rings. Plaster is porous: if it isn't protected, it absorbs water and moisture, stains and weakens over time.

In this guide we look at how Aqua Shield works, which dosage to use and which of the three methods to choose for your project. If you're just starting out, also read the most common mistakes when working with plaster: skipping protection is one of them.

Contents

• Key points
• Why plaster needs protecting
• What is Aqua Shield
• Method 1: in the mix
• Method 2: brushed on
• Method 3: dipping
• Which method to choose
• Common mistakes
• Recommended products
• FAQ

Key points

• Aqua Shield can be used in three ways: in the mix, brushed on or by dipping.
• In the mix it replaces water: 50 g per 100 g of Aqua Resin, 60% of the weight for natural plaster.
• With Aqua Shield in the mix, demoulding takes at least 1 hour; full drying takes 24 hours.
• Aqua Resin is not an epoxy resin: it is a premium alpha plaster, non-toxic and water-based. Aqua Shield is water-based and odourless too.

Why plaster needs protecting

Porosity is what makes plaster so pleasant to colour and finish, but it is also its weak point. A drop of water can leave a stain that's hard to remove, candle wax soaks into the surface, and a damp room like a bathroom can weaken the piece over time. Protecting it extends the life of your creation and makes it functional, not just decorative.

What is Aqua Shield

Aqua Shield is a water-based, non-toxic, odourless additive that makes plaster creations resistant to water, stains and moisture. It is designed for Aqua Resin, our premium alpha plaster, but it also works with synthetic plasters and natural plaster.

As well as protecting, it gives the surface a smooth, glossier finish that feels pleasant to the touch. Once applied it is transparent, but it slightly changes the colour: keep this in mind, especially on coloured pieces.

Method 1: Aqua Shield in the mix

This is the most protective method, because Aqua Shield becomes part of the structure of the piece instead of staying on the surface. Choose it when the creation is designed for water from the start: vases, candle holders, soap dishes, coasters.

1. Weigh the powder and Aqua Shield on a scale: guessing quantities is the main cause of fragile pieces.
2. Pour Aqua Shield into a container and add the powder, sifting it in slowly.
3. Mix with an electric whisk for about one minute, until fluid and lump-free.
4. Pour into the silicone mould and tap the mould on the work surface to release air bubbles.
5. Demould after at least 1 hour and let the piece dry for 24 hours before use.

Pro tip: to colour the mix, add Aqua Pigment to Aqua Shield before adding the powder: the colour spreads more evenly.

Method 2: Aqua Shield brushed on

The brush method is used on a piece that has already been demoulded and is completely dry. It's the right choice for protecting pieces you've already made, for treating only the inside of a vase or candle holder, or when you don't want to change your usual mix.

1. Wait until the piece is dry: at least 24 hours after demoulding.
2. Remove any dust with a soft, dry brush.
3. Apply Aqua Shield in a thin, even layer, focusing on the areas that will be in contact with water.
4. Let it dry before using the object.

Method 3: Aqua Shield by dipping

With the dipping technique, the dry piece is immersed in Aqua Shield, so the product reaches corners and fine details that are hard to treat with a brush in a single pass. It also works on traditional plaster, so it's useful for protecting pieces made in the past.

1. Pour Aqua Shield into a container wide enough to hold the piece.
2. Dip the dry piece, then lift it out and let the excess drip off.
3. Place it on a clean surface and let it dry before use.

Pro tip: dipping is the quickest way to protect lots of small pieces at once, such as a set of party favours or place cards.

Which method to choose

For a vase that will hold water, the safest option is mixing in Aqua Shield. You'll find suitable shapes in our plant pots and planters collection. For candle holders, see our guide to DIY candles and candle holders.

Common mistakes

• Adding water as well as Aqua Shield. In the mix, Aqua Shield fully replaces water: adding more makes the piece weaker and less protected.
• Demoulding too early. With Aqua Shield in the mix you need at least 60 minutes, not the usual 30.
• Treating a piece that is still damp. Brushing and dipping must be done on a completely dry piece, otherwise the protection won't bond evenly.
• Using it in scented plaster. Aqua Shield closes the pores and blocks the fragrance: avoid it in scented plaster.
• Forgetting the glossy effect. If you want a matte finish, test on a sample first.

Recommended products

• Aqua Shield — the water-based additive for waterproofing plaster, in the mix or on the surface.
• Aqua Resin — premium alpha plaster, porcelain-white, demoulds in about 30 minutes.
• Aqua Resin Terracotta Roma — the same alpha plaster in terracotta, ideal for vases protected with Aqua Shield.
• Aqua Resin Black — black alpha plaster for bold design objects.
• Aqua Pigment — concentrated liquid pigments for colouring the mix, including with Aqua Shield.

FAQ

How much Aqua Shield do I need for 100 g of Aqua Resin?

You need 50 g of Aqua Shield for every 100 g of Aqua Resin. Aqua Shield fully replaces the water: do not add any extra water to the mix.

Does Aqua Shield work with traditional plaster?

Yes. Mixed in, it is dosed at 60% of the weight of natural plaster (60 g per 100 g of powder) and at 50% for synthetic plasters. On pieces already made in traditional plaster, it can also be brushed on or applied by dipping.

When can I demould a piece made with Aqua Shield in the mix?

With Aqua Shield in the mix, demoulding takes at least 1 hour, instead of the 30 minutes needed when Aqua Resin is mixed with water. Full drying takes 24 hours.

Does Aqua Shield change the colour of my creations?

Aqua Shield is transparent, but it slightly changes the colour and makes the surface glossier. Before treating an important piece, test it on a sample first.

Can I use Aqua Shield for candle holders?

Yes. Aqua Shield makes candle holders resistant to water and wax, and it is one of its most common uses.

Can I use Aqua Shield in scented plaster?

No. Aqua Shield closes the pores of the plaster and stops the fragrance from spreading: avoid it in scented plaster, both in the mix and on the surface.

Ready to make creations that stand up to water?

Choose the method that suits your project and start from the right base: Aqua Resin for creating in silicone moulds and Aqua Shield to protect every piece. To see why alpha plaster gives better results than ordinary plaster, read our comparison plaster vs alpha plaster.
→ Discover Aqua Resin