How to Work with NATURESIN: Step-by-Step Casting Without Bubbles or Chips

The pour looks smooth, the mixture has spread nicely through the mold, and everything seems to have gone to plan. Then you demold the piece and find small holes on the visible surface and a chip missing from the thin rim. The frustrating part is that these defects only become visible once most of the work is done.

With NATURESIN, the first few minutes have a major influence on surface quality. Measuring the water, mixing the powder, filling the mold details, and releasing trapped air all affect the finished result. Keeping the edges intact also depends on how long you leave the casting before demolding and how you peel away the silicone.

We will walk through the process using a small coaster or a tray with a low rim. This is a useful starting point: it lets you practice creating an even surface and neat edges before moving on to more complex vases and figurines.

What to know about NATURESIN before your first pour

NATURESIN is an acrylic composite supplied as a mineral powder that you mix with water. Once hardened, it produces a solid, opaque piece with a surface reminiscent of stone or ceramic.

The material sets quickly, so prepare your mold and tools before mixing. While you are looking for a brush or clearing space on the table, the mixture is already changing consistency.

It helps to think of the process in three stages:

• Working time: a short window for mixing, coloring, and pouring. Aim to complete the main tasks within approximately 10–12 minutes of starting to mix.
• Demolding readiness: the casting holds its shape but still needs careful handling. You would usually make the first check about 40 minutes after pouring.
• Further hardening and drying: the piece continues to gain strength after it leaves the mold. Sanding and finishing come later.

These times depend on temperature, the formulation, and the shape of the piece. Forty minutes may be too soon for a thin rim. Do not rush to demold simply because the timer has gone off.

Step 1. Prepare your workspace, mold, and tools

Place the mold on a firm, level surface. A small board or tray works well beneath a flexible mold: if you need to move the casting, you can move it together with its base without distorting the piece.

Check the table with a spirit level. If the base slopes, the mixture will collect on one side, leaving the bottom and rim uneven in thickness.

Before you begin, prepare:

• NATURESIN and clean water at room temperature;
• digital scales;
• a clean mixing container with enough spare capacity;
• a spatula or stirring stick that can reach the bottom and sides;
• a silicone mold;
• a small, soft brush for recesses and surface details;
• a powder pigment if you plan to make a colored casting;
• paper towels and a protective mat for the table.

Arrange your NATURESIN tools within easy reach. The container should allow you to stir calmly without spilling the mixture over the edge.

Transfer the powder gently, without creating a dust cloud. After working, wipe up residue with a damp cloth. Store the powder tightly sealed and away from moisture.

Step 2. Check the silicone mold

Inspect the inside of the mold in good light. Dust, lint, residue from a previous casting, and damaged silicone can all leave marks on the finished piece.

The mold must be clean and dry. If you have washed it, allow the recesses and folds to dry as well. Do not coat it with an unsuitable oil: this can alter the casting's surface and interfere with later painting or coating.

For your first project, choose a silicone mold for NATURESIN with a simple shape and moderate surface detail. Very thin projections, narrow channels, and deep undercuts require more care when pouring and demolding.

Remember that the visible face of a coaster is often at the bottom of the mold. The mixture can look perfect from above even when air is trapped against the silicone. That is why bubbles need attention during the pour.

Step 3. Calculate and weigh the components

Measure NATURESIN and water by weight, in grams. A measuring cup cannot replace scales: the volume of loose powder depends on how densely it is packed.

For the calculations below, we use a ratio of 100 parts powder to 27 parts water. This means that every 100 g of NATURESIN needs 27 g of water.

If your packaging specifies a ratio of 100:30, follow that ratio: for example, 200 g of powder will require 60 g of water. Choose the ratio specified for your material, rather than changing it to obtain the consistency you want.

The amount of mixture you need depends on the mold's capacity. The example using 200 g of powder explains the calculation; it does not mean that this amount will fill every coaster or tray mold.

If you have used the mold before, record how much mixture it takes and use that figure for future projects. For a first attempt, it helps to have a small extra mold ready for any leftover mixture.

Extra water makes the mixture thinner, but it can reduce the strength and surface quality of the finished piece. Avoid adding water by eye just to make pouring easier.

Step 4. Add the powder to the water and mix thoroughly

Pour the measured water into the container first. Then gradually add the weighed powder while stirring.

Adding all the powder at once makes it harder to achieve an even mixture: dry pockets and lumps may remain. Adding it in small portions helps wet the material evenly.

Continue mixing for approximately two minutes, working along the bottom and sides of the container. Use calm movements without whipping the mixture or creating a deep vortex. The aim is a smooth, flowing mixture without lumps, while introducing as little air as possible.

The finished mixture has a consistency similar to runny sour cream. Its appearance is not a substitute for measuring the components accurately: a correctly weighed batch should become uniform after thorough mixing.

Do not add water to make a mixture flow again once it has started to set. If it thickens noticeably, loses its uniform texture, and no longer spreads well, prepare a fresh batch. Trying to save the remainder this way can spoil the whole project.

Step 5. Color the mixture with powder pigments

Powder pigments are the best choice for coloring NATURESIN. Add the pigment powder while mixing the material with water and distribute it thoroughly throughout the batch. Work along the bottom and sides of the container so the casting does not have colored specks or unwanted streaks. Measure out the pigment in advance: coloring is part of the mixture's total working time.

This method usually gives the piece a pleasant pastel shade. NATURESIN powder has a pronounced white color of its own, which noticeably lightens the added pigment. A deep, saturated color is difficult to achieve throughout the material: the finished casting will look softer in color than the pigment in its jar.

Do not keep increasing the amount of pigment without regard to its recommended dosage in an attempt to intensify the color. Follow the dosage for your chosen pigment and test the shade in a small trial casting first. Record the quantities of powder and pigment so you can reproduce the result.

Do not use liquid epoxy resin colorants that are designed to cure together with the resin. They do not harden on their own and can leave uncured, sticky areas in NATURESIN. Choose pigments compatible with acrylic composites for coloring the mixture.

You can also paint the finished piece with acrylic paints. Wait until the casting has fully hardened and dried, remove any sanding dust, and only then apply the paint. This is a useful way to add a bright design or rich color accents to a soft pastel base.

Step 6. Fill the details and recesses first

Small holes on the visible surface often have one cause: the mixture did not displace the air in a recess of the mold. This is especially noticeable around rims, in corners, and in fine surface details.

Before the main pour, spread a small amount of fresh mixture over these areas. Gently work it into the details with a soft brush so the material reaches the recesses and displaces trapped air.

For a tray with a rim, pay attention to the point where the base meets the wall. An air pocket here can look like a small chip, even though the area simply failed to fill with mixture.

Proceed with the main pour straight away. The thin layer and the remaining mixture need to join while both are still fresh. There is no need to dry the first layer separately for this type of casting.

In a simple, smooth mold, this step takes very little time. The more detailed the mold, the more useful it is to plan the sequence in advance and avoid distractions after mixing.

Step 7. Pour into the mold and help the air escape

Bring the container close to the mold and pour a steady stream into one chosen point. Let the mixture spread gradually through the mold. Pouring from a height or moving the stream randomly between different areas can introduce more air.

Once the mold is filled, gently tap its sides and lightly tap the firm base against the work surface a few times. You can also give it a few short, gentle rocking movements. The mold should keep its shape and the mixture should stay inside.

Watch the surface: you can carefully pop bubbles that rise with the tip of a stirring stick. A smooth top does not prove that there is no air against the visible face, though. Filling the details first and releasing air after pouring both matter for a clean result.

Do all of this while the mixture is still flowing. Once it starts to set, stop tapping, rocking, and adjusting the casting.

You do not need a torch or a heat gun for this process. Air is removed through careful mixing, filling the mold, and gentle vibration.

Then leave the mold on its level base. Do not lift it by its flexible edges or check every few minutes to see how hard the material has become.

Step 8. Demold without damaging the edges

After approximately 40 minutes, you can carefully check whether the piece is ready to demold. If the casting is still soft or the thin areas seem fragile, give it more time. Colored mixtures and complex shapes may need a longer wait.

Start with an easy section of the mold. Gradually peel the silicone away from the piece, supporting the casting with your hand or a flat support. Release the rim around its perimeter without a sudden pull.

Do not pull a tray out by its thin edge, bend it, or pry it free with a knife. Even if the main body feels hard, projections and thin walls are still vulnerable at this stage.

If the mold is difficult to remove, stop and check which area is still held by the silicone. Using more force rarely helps preserve fine details.

For your first project, allow extra time for setting and demolding. A few rushed minutes can cost you an entire rim.

Step 9. Let the piece dry and finish the edges

After demolding, the piece continues to harden and release residual moisture. At this stage, the surface may look darker or uneven in color. Judge the final shade once the casting has dried.

Place the piece on a flat support in a dry room with normal air circulation. Do not stack fresh castings or seal them in airtight packaging. Avoid direct sunlight, heaters, and intense heat.

For a first project, it is convenient to leave the piece until the next day before finishing. A thicker casting or high humidity may require more time. Check that the piece has dried and follow the times specified for your batch of material.

Once the piece has fully hardened, remove uneven areas on the back with fine-grit sandpaper. Use light pressure, especially near corners. Sanding a thin rim immediately after demolding increases the risk of chips.

When dry sanding, avoid breathing in dust, use appropriate protection, and clean the workspace with a damp cloth.

A clean visible face usually does not need the same treatment as the back. Whether the surface is matte or glossy depends partly on the inside of the mold: sanding will change that effect.

Before applying a protective coating, wait for the piece to dry and remove dust. For coasters, trays, and other items that will regularly come into contact with moisture or dirt, choose a compatible coating suited to the intended use. Allow the coating itself to dry for the required time as well.