5 Things You Should Know About The Transition From Solvent To Water-Based Coatings

Key things to be aware of and look out for when considering a change from solvent to water-based coatings

1. Eliminate Solvent Contamination

2. Select The Correct Tip Size

3. Understand The Differences in Appearance

4. Prepare For The Perfect Finish

5. Consider Drying Conditions

Acetone will typically be the solvent of choice used when making the switch. Whether you are hand spraying or using an automatic sprayline, the step will be to thoroughly flush the paint lines with Acetone.

Standard thinners or Gunwash are not advised to be used at this point as it is not always strong enough to remove any remaining debris, and is harder to remove with water in the next step.

IMPORTANT: After Acetone, be sure to thoroughly flush the paint lines with clean water.

If the hoses are relatively old or have had a lot of solvent-based coatings build-up, it is  best practise to change to brand new lines, this avoids any blockages due to the build-up of solvent debris that has occurred over time.

The next thing to look at will be your new tip size – this may need to be larger than your current one due to the water-based coatings typically having a higher viscosity.

For hand spraying, a 1.8 tip is normally recommended in order to atomise any water-based material.

With an autoline, depending on the manufacture of the guns, this would typically be 13/40  (13 thou orifice, 40 ° fan angle).

In addition to this, we would advise replacing all filters in order to avoid any cross-contamination.

When spraying water-based coatings, one of the main differences to solvent-base material is how it appears on the substrate immediately after spraying.

When wet, water-based can have an ‘orange peel’ look to it at first - not something you would normally see with its solvent counterpart.

Once left to flash off for 10-15 minutes, this will flow out to a perfectly flat finish, due to the flow additives that are present in water-based technology.

When spraying substrates  such as MDF, the first coat of primer will look very different when using water-based compared to a solvent-based paint.

This is due to the  water-based primer tending to raise the MDF fibres initially, giving a ‘wood chip wallpaper’ type appearance.

After sanding (with 240grit) and a second coat of primer, this will have completely gone and the finish should be perfectly flat.

Drying time is where you may see the biggest difference between solvent and water-based products.

A solvent-based product can rely on chemical reactions and forced heat to provide a fast cure, whereas a water-based paint relies heavily on airflow and controlled temperature.

With this in mind, if you currently use a drying room or heat box with limited or no air movement, this will need some adapting. This could simply be the addition of a plug-in fan to generate some air movement.

If there is some air movement present, water-based coatings only really need temperatures of 18C or above to provide adequate drying conditions.