How do you make colour matching gelcoat?

In order to achieve an almost invisible gelcoat, the new gelcoat to be applied must have the exact colour of the surrounding gelcoat. It is often not possible to achieve the same colour. In this article we explain how you can make colour matching gelcoat yourself and we provide some useful tips. Using our gelcoat, topcoat or gelcoat filler, in combination with various polyester pigments, you can easily make colour matching gelcoat. 

Supplies

You will need the following materials:

• Gelcoat, topcoat or gelcoat filler, in clear or white or a colour close to the colour to be repaired.
• Polyester pigments (the pigments required vary per project).
• Mixing cups
• Mixing spatulas
• Sandpaper (1500 grit)
• RIWAX RS 08 wax
• Acetone

To perform a gelcoat repair, you will need the following materials:

• Hardener
• Thick foil
• Brush and fleece roller
• Sandpaper (grit 400 / 600 / 800 / 1000 / 1200)
• Polishing compound RIWAX RS02, RS06 and RS08
• Possibly a polishing machine

How are polyester products affected by the environment?

As soon as a polyester product, such as a boat, camper or gutter, is released from the mould, it is affected by the environment. The product is continuously exposed to light, water, pollution and temperature. This will change the colour of the product. 

• Light: causes oxidation and yellows some colours.
• Water: a universal solvent that, by attacking the surface, causes porosity and stains.
• Polution: pollen, spores, mold, acid rain, smog are all factors that can bleach or leach colours.
• Temperature: high temperatures cause colours to yellow, chalk and fade.
  • White colours yellow and chalk.
  • Blue and green colours fade and chalk.
  • Red and yellow colours turn brown or darker.

What are the right conditions to see and judge colours?

Colour is the brain's interpretation of what the eye sees. Because it is an interpretation, we must keep as many factors constant as possible every time we colour gelcoat. This ensures a better assessment of the colour and therefore gives better results.

Please note the following when colouring gelcoats:

• The person who makes the colour gelcoat must not be (partly) colour blind.
• A cold, fever, flu, eye infection, hangover or simply having an “off day” can affect the assessment of colour.
• In many situations, two people's judgment can yield better results.
• If possible, use northern lights. This light is shadowless and displays colours best. Stand with your back to the north, with the workpiece to the south.
• Never use artificial light or too bright light.

When evaluating the colour of the gelcoat (which is in colour) and the object (where the colour of the counterfeit should be made), the following aspects should be considered:

• The light reflected from the object is white.
• The light absorbed by the object is black.
• When all light is absorbed by the object except red, then the object is red. This also applies to all other colours.

You must be able to judge the difference between the colour of the gelcoat and the object. This is divided into 3 categories:

• Depth: this describes whether the colour is lighter or darker.
• Colour dominance: this describes whether the colour is redder, bluer or more yellow.
• Grayscale: this describes whether the colour is grayer or brighter.

Important:

• Red objects can only have a blue or yellow colour dominance.
• Blue objects can only have a green or red colour dominance.
• Green objects can only have a green or red colour dominance.
• White, gray and black objects can have a green, yellow, red or blue colour dominance.

Order colour matching gelcoat 

If a polyester product, such as a boat, a scooter hood or a camper, is less than 2 years old, the correct colour gelcoat can often be reordered from the manufacturer. Because the product's gelcoat is not yet discolored or weathered, a repair can still be carried out almost invisibly with the manufacturer's gelcoat. So you don't have to create this colour yourself.

If the gelcoat is no longer available or if the polyester product is older than 2 years, you must colour match the gelcoat yourself. In this case, a good quality gelcoat can be used in combination with polyester pigments.

How do you make colour matching gelcoat?

Step 1. Prepare the surface

First of all, you should thoroughly clean the surface on and around the repair site. Wash away the contamination and sand the surface with 1500 grit to remove chalk, oxidation and contamination. If possible, sand an area of ​​30 x 30 centimetres directly next to the repair. We are going to use this to colour the gelcoat. Wax the sanded surface. This largely brings back the shine. 

Step 2. Choose the base colour

After you have properly prepared the surface, you can use a RAL colour chart to see which colour corresponds to the correct gelcoat. If a colour matches, you can order this colour very easily. Unfortunately, a colour fan may also differ slightly, so the colour of the gelcoat may also need to be adjusted slightly.

Is the exact colour not available? Then choose a colour that most closely matches the shade, possibly slightly lighter than the original. For light colours, a white gelcoat can often be used.

Step 3. Make colour matching gelcoat

Take a generous amount of gelcoat, which is definitely enough for the repair. Making exactly the same colour a second time is almost impossible. So be sure that you make enough colour gelcoat. Please allow 50 grams extra for colouring.

Pour the gelcoat into a mixing cup and use a mixing spatula to a little gelcoat to the substrate where the colour is to be imitated.

Now stand back and observe the colour difference:

• If the surface is lighter than the gelcoat, add white pigment.
• If the surface is darker than the gelcoat, add the dark base colour.
• For colour dominance, use the following table:

How do you add pigment?

Determine which colours of pigment are needed for coloring. These are often black, the dark base colour and possibly other colours. For white objects it is often black, yellow and ochre or brown.

Take a stirring stick/mixing spatula and apply some pigment halfway through the stirring stick. To add the pigment to the gelcoat, follow the following procedure:

• Hold the stirring stick with pigment above the mixing cup.
• Using a second stirring stick, apply gelcoat to the stirring stick with pigment and mix the gelcoat into the pigment. This way you have control over the amount of pigment that is added.
• Allow the colored pigment to flow into the mixing bowl and mix thoroughly. Once again you can determine whether enough has been added. Leave the remaining gelcoat on the stirring stick.
• Now apply the added pigment to the surface, in addition to the previous attempt, and determine the deviation again.
• Then choose the next colour to add. You often have to add the same coluor a number of times until that colour dominates.
• Then choose another colour to add. Continue to use the table above. This way you can work towards the right colour in small steps.

Tips for making colour matching gelcoat:

1. Add small amounts of pigment at a time, for minor colour corrections. This way you achieve a better and more accurate result. It is not uncommon to make 25-30 colour corrections.
2. A second person can help judge the colour. It can also help to leave for a while and come back after a few minutes.
3. Do not aim for absolute perfection, but for a colour that no longer makes the repair noticeable. Even an expert won't be able to duplicate the exact colour. Ultimately, every repair can be seen under the right circumstances.

Step 4. Finishing and polishing

Once the gelcoat has the right colour, you can clean the surface with all colour samples with a cloth and acetone. This also removes the applied wax. You can then carry out the repair and polish the product.

More information?

In the article above you could read how to colour gelcoat so that your gelcoat repair has the same colour as the rest of the gelcoat and is therefore no longer noticeable. Good luck! Do you have any questions or do you need advice? Please do not hesitate to contact our specialists. They are happy to help you make your project a success.