‘Plasticizer Migration’: What Is It? How Do You Fix It?

Are you ready for another finish anomaly article? This one’s different—it’s something that isn’t your fault, and you can’t prevent it. But being informed is key, so when you get that dreaded phone call, you’ll know what it is, how to explain it to your client, and, most importantly, how to fix it.

In my last article, I wrote about tannin pull when using waterborne finishes. This time, I’m sticking with the theme and diving into a lesser-known issue: plasticizer migration. This anomaly is rare, and in my experience, it only shows up with waterborne finishes.

What Is ‘plasticizer migration’?

Let’s start with the basics, because most wood flooring professionals haven’t encountered this term. Plasticizer migration happens when plasticizers—chemical additives used to increase flexibility and durability in materials like plastics, rubber and coatings—move out of the material they’re embedded in and transfer onto adjacent surfaces. Factors like heat, aging and chemical interactions can accelerate this process.

These spots were from rubber pads under folding chair legs that created plasticizer migration in the waterborne finish.Why can’t you prevent it?

The frustrating part is that not all plastics or rubber products contain plasticizers, which makes it nearly impossible to tell homeowners exactly what to avoid. Plasticizers are used to improve flexibility, prevent cracking and extend product lifespan, but not every material needs them or uses them.

I’ve personally seen plasticizer migration come from various sources, including chairs with plastic feet, rubber area rug pads and even plastic-wrapped dumbbells.

What speeds it up?

Several factors can accelerate plasticizer migration:

• Heat: High temperatures can make plasticizers leach out faster.

• Aging: As materials break down over time, migration becomes more likely.

• Harsh chemicals: Strong cleaning agents can speed up the deterioration of plastic materials, pushing plasticizers into the finish.

How to spot plasticizer migration

When plasticizer migration occurs, you’ll see dark marks on the floor. Unfortunately, this creates a permanent bond with the finish that can’t simply be cleaned off. The only solution is to remove the damaged finish and reapply fresh layers.

How to repair plasticizer migration

Here’s what I’ve found works best for repairs:

1) Assess the damage: Migration usually stays in the finish, but on rare occasions, it can touch the surface of the wood. It doesn’t penetrate deeply, so keep that in mind when deciding your approach.

2) Carefully remove the finish: Use a sharp scraper to lightly remove the finish, being cautious not to gouge into the wood. Follow up with 120- or 150-grit sandpaper for a smooth surface.

3) Reapply finish in light coats: Build the finish back up using several light coats instead of one heavy coat. This ensures a more even repair and avoids issues with adhesion.

4) Set realistic expectations: Let the homeowner know this is a spot repair—it’s about improving the appearance, not achieving perfection. When you’re done, step back 6 feet. If it looks good from there, you’re golden.

The non-skid pad under an area rug, shown at right, created this pattern in the waterborne finish. 

Final thoughts

Plasticizer migration might be rare, but it’s good to have this knowledge in your toolbox. Being able to identify the issue, explain it to your client and confidently handle the repair sets you apart as a professional. The next time you see one of those mysterious dark marks, you’ll know exactly what it is and what to do.