When to Apply Isolation Coats to Acrylic and Oil Paintings: Best Practices and Tips

For artists working with acrylic and oil paints, applying an isolation coat is an essential step to protect your work. However, determining the right timing for this application can be tricky. In this article, we will explore common scenarios and provide guidance on when to apply an isolation coat to ensure the best results.

Understanding the Importance of an Isolation Coat

An isolation coat acts as a protective layer between your base paint and the varnish or final coating. It helps prevent any chemical reactions or other issues that could interfere with the varnish's adhesion to your artwork. While acrylic paint dries much faster than oil paint, there are still considerations to keep in mind when applying an isolation coat.

Acrylic Paintings: When Is It Safe to Apply the Isolation Coat?

When working with acrylic paints, a common question arises: should the isolation coat be applied immediately after the paint has dried to the touch? The general consensus is that this is usually fine, as acrylics dry very quickly and their binder becomes stable rather quickly.

However, there are a few scenarios where extra caution is advised:

If you have applied the paint super thickly with a knife or if you have created a poured paint art with flow additives or mediums like oils and alcohol, it's possible for the piece to feel dry but still 'sweating' compounds for days. An isolation coat applied too soon might trap chemicals separating from the paint and support, leading to a haze.

It is recommended that the Golden brand provides a guidance of applying the isolation layer after 24 hours, or one day. However, in many cases, the paint being dry to the touch is a good indicator that the isolation coat can be applied.

Oil Paintings: When to Worry About the Isolation Coat

For oil paintings, the application of an isolation coat is also crucial but for different reasons. Unlike acrylics, oil paint takes longer to dry because the binder is oil, which polymerizes over time rather than evaporating. Applying an isolation coat too soon could cause it to crack as the layers of oil continue to dry at different rates.

Oil paints don't technically "dry" in the same way that acrylics do; instead, they polymerize, forming long chains that change the paint's consistency and appearance over time. If the lower layers contain more oil and take longer to dry than the upper layers, you may experience cracking due to the top layer drying faster.

Therefore, it is highly recommended that you give your oil painting a minimum of 24 hours to fully cure before applying the isolation coat. This allows the paint to stabilize and reduces the risk of cracking when the isolation layer is applied.

Best Practices for Applying Isolation Coats

To ensure the best results when applying an isolation coat, follow these tips:

Wait for your painting to dry to the touch before applying the isolation coat, but always check for any ongoing chemical reactions or 'sweating.' To avoid trapping chemicals, wait a minimum of 24 hours, or one day, before applying the isolation coat, especially if your painting involves thick applications or flow additives. Once the isolation coat is applied, wait for a few days to ensure it dries fully before applying varnish or sealing the work. After the painting has fully 'cured,' or a few days have passed, use a soft brush to remove any loose brush hairs and dust. Utilize a magnifying glass to inspect the painting and ensure that it is clean and free from any unwanted particles before applying the isolation coat.

Remember, learning from mistakes is an invaluable part of the creative process. If you find that you have applied the isolation coat too early, be patient and let the painting rest.

For more detailed advice and product recommendations, consult with fellow artists, art supply retailers, or the manufacturers of your chosen isolation products.