What causes Paint Solvent Popping? and how to stop it

Jun 25


Andy Potts

Andy Potts

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Paint solvent popping can easily ruin any professonal or ameteur spray or paint job. The tiny raised bubbles in your paint job are a tell tale sign you have solvent popping and there is no easy cure to returning your paint finish back to pristine.


Author Andy Potts | 25th June 2020 | Reading time approx 2 mins 


What Causes Paint Solvent Popping? 

Thinners or reducers being trapped in the paint film due to inadequate flash time between coats,What causes Paint Solvent Popping? and how to stop it Articles too much air movement causing surface to skin over.


If your paint finish is no longer flat and smooth and instead you have tiny bubbles forming like a crater of mountains, then you likely have solvent popping.


This is called solvent popping. It is when thinners or reducers become trapped in the paint film . The surface then drys and the surface layer skin drys too quickly. The result, particles of thinner that can't escape from under the paint coating by evaporation or general movement.

The main issue of trapped thinners is evaporation, the mix of top coat and trapped thinners unable to escape to atmosphere leaves bubbles or craters. As they can't evaporate the only alternative is to push through and pop the surface.


Why does Solvent Popping occur?

This happens when there is inadequate flash time between coats, (Flash time isn't a super hero thing, it's actually the necessary waiting time taken before you can expect to lay down a new coat of paint upon the last.) Flash time in itself can cause solvent popping issues. 

A long Flash time means a requirement to scuff back or sand back your paint job before recoating to avoid issues. If you fail to scuff back it's likely you may see solvent popping on your second coat even if you don't get it on the first. 

A short Flash time measn you may not need to scuff back but the shorter time period between coats raises the likelihood that the initial layer and secondary layer could react with each other and again cause solvent popping. 

A further cause of popping is air movment, too much air passing over a surface be it natural breeze or man made such as a fan or heater will cause the surface to skin over, the paint is being applied to thickly or too much flash time before force drying.


Can you repair Solvent Popping? 

If you only have minor solvent popping - watch this guide to see the differences between a lot and small amounts of popping, then you may only have a limited amount of work to rectify. The best course of action would be to allow the finish to thoroughly cure and then sand it smooth and begin the re-coating process again to refinish. This may be frustrating but no potential customer is going to accept a job with ugly solvent popping as a good job - don't forget it's your reputation on the line here! 


 If, however the popping has occurred in large areas then you will have to remove the affected film by block sanding, clean the area to allow you to fully re-prime, seal and recoat with a approapriate topcoat where necessary.

It's worth noting here that popping can occur in any paint job it isn't a one industry issue so you may find it rears it's ugly head in anything from car refinisihing to steel fabrication painting or even wood painting but it does help to use top brands to avoid the likelihood such as Sayerlack for wood and Jotun Paints for Metal.


How do I stop it happening again?

To prevent solvent popping appearing on every paint job you start you need to follow a few crucial steps. These 4 main steps will ensure you get the best finish.

  1. Firstly, select the recommended thinner or reducer based on the temperature, humidity and air movement. Thinner is crucial and there are many types. For example a standard thinner may contain waste products in it that contains partciles, dust and waste from other recycled applications. USe high quality Xylene thinners for a better finish.
  2. Next, avoid double wet coats - Placing a layer of paint over a still wet layer of paint will pull or curl the initial layer. Once the first layer curls air can become trapped between the two coats causing solvent popping. 
  3. Thirdly, allow for proper flash times between coats. Maintain the recommended flash time. Re-coating before a flash time can result in wet layers and solvent popping. Recoating after a flash time can result in a rough surface that needs flatting and again solvent popping can occur. 
  4. Finally, restrict the air movement over the surface that you are painting. This is because air might go into the paint film, air then becomes trapped when the surface layer dries.


If you ensure that all these points are covered in your paint shop, then the chances of solvent popping are going to reduce hugely.