6 Ways How to Fix Sanding PLA Turning White – 3D Prints

Sanding is a crucial step in 3D printing since it helps prints to achieve a smooth and polished finish. However, PLA can get unwanted white spots or streaks when you sand it, ruining the quality of your finish. That is why I wrote this article to explain some of the ways you can fix this.

To fix sanding PLA turning white, use higher grit sandpaper, wet sand your print, heat polish the print, or apply a small amount of mineral oil over the sanded area. You can also wipe the sanded area using Acetone, Vaseline, or use a clear coat spray.

This is an overview of the best methods to fix this problem. I will provide details about each method, so stick around to learn more.

How to Fix Sanding PLA Turning White

Here are some of the main ways you can fix sanding PLA turning white:

1. Use higher-grit sandpaper
2. Wet sanding
3. Heat/flame polishing
4. Apply mineral oil or Vaseline over the sanded area
5. Use Clear Coat spray
6. Wipe with acetone

Note: You might need to combine some of these methods for the best results.

1. Use Higher-Grit Sandpaper

One of the most common methods of fixing sanding PLA turning white is using higher grit sandpaper. When you sand with a lower grit sandpaper, the PLA surface may become rough and scratched, leaving white spots.

You can easily fix this using higher grit sandpaper, which gives you a smoother and more refined finish. This makes the white parts less visible.

Start with 400 to 600-grit sandpaper and apply light pressure to avoid generating too much heat that can warp the PLA. Gradually progress to higher grit sandpapers to create a smoother surface and remove the white spots.

One user said that sanding often turned most of his plastic white. He said it could be due to plastic clinging onto the rough surface when you don’t clean your prints after sanding.

To fix this, he follows up the rougher sanding with extra fine sandpaper (600-grit or finer, maybe even as fine as 1,500), which polishes the surface and removes the rough surface. This helps the plastic to go back to its original color.

Another user wanted to know how to fix PLA turning white after wet sanding it. Someone responded that using a higher grit sandpaper will bring back the color and give the PLA a nice polished shine.

2. Wet Sanding

Another effective method of restoring the original color of PLA after it turns white due to sanding is wet sanding. For this method, you only need to dip the sandpaper in a bowl of water for a few seconds before sanding your model.

After that, rinse off your model and repeat the process until you get the desired look. Always ensure you use sandpaper designed for wet sanding (you can check the package it came with).

Sanding often generates a lot of friction, removing material from the outer surface and leaving white streaks or powdery stuff on the surface. This hides the color of your print.

However, wet sanding keeps the PLA surface and sandpaper well-lubricated, minimizing the abrasive action of the sandpaper. Additionally, water cools the surface of the PLA during sanding, allowing it to maintain its original color.

One user recommended finishing with grits between 1,000 – 2,000 and wet sanding. What he does is mix soap or dish soap when wet sanding. This helps the texture of the print to return to what it was when you started printing and, in turn, returns the color to how it was.

Another user always got a white frosty finish after he sanded PLA. To fix this, he wet-sanded his print with 200-grit sandpaper up to 24,000 in about 9 stages. This gave his bare PLA a glossy, smooth, and perfect look.

Several users recommended using finer grit sandpaper and wet sanding to remove any white spots and return PLA to its original color.

3. Heat or Flame Polishing

Heat or flame polishing can help an object printed with PLA and then sanded to regain its original color. However, for this method to work, you must use a controlled heat source such as a heat gun, hair dryer, or handheld butane torch.

This 1800W SEEKONE Heat Gun you can find on Amazon would work just fine.

One user said that he was genuinely blown away by how much he could get done with this for how little it cost. He added that it had a really huge range of temperatures and was good for getting things done.

Another user said this heat gun is a must-have, especially at this price point, and would highly recommend it. Its temperature control was worthwhile, and the simple stand worked well. Additionally, the gun heated up quickly and had two fan speeds.

When you carefully heat your object with the SEEKONE heat gun or any of the tools above, a thin layer of the surface softens and starts to flow slightly.

As the PLA begins to cool, the melted layer will smoothen, removing the white color. Always avoid applying too much heat, as it can completely melt your print.

One user said they used a heat gun from a soldering station to carefully heat the PLA, ensuring it didn’t get too hot to melt. They also used a blowtorch successfully before. The only trick they used was to move the flame quickly over it and from a distance.

Another user said that a good way to fix PLA that has turned white after sanding is to flash the sanded area with heat. He added that you could use a heat gun or small flame in a quick motion across your piece without pausing in any one spot for too long.

Someone else said that they bought a handheld butane torch used for baking, and it worked great, leaving his prints with a nice finish.

4. Apply a Small Amount of Mineral Oil or Vaseline Over the Sanded Area

An unconventional way of fixing sanding PLA turning white is to apply a small amount of mineral oil or Vaseline. Put a small amount of mineral oil or Vaseline in a clean cloth and gently rub it over the sanded PLA surface. Ensure it covers all the affected areas.

You can try this Swan Mineral Oil, which is available on Amazon.

Sometimes PLA’s texture becomes too rough on the surface after sanding as it develops micro scratches. This can scatter light and make it appear white or pale.

Rubbing the mineral oil or Vaseline on its surface fills these micro scratches, making the surface smoother. Ultimately, this scatters the light less and helps PLA regain its original color.

However, most 3D printing enthusiasts recommend this method as a temporary fix. This is because you might need to occasionally reapply the Vaseline or mineral oil to maintain the restored appearance.

One user said that he had seen some commenters on various forums using a very light application of mineral oil over the abraded area. After trying this method twice, the original color of his PLA returned.

A user who worked for a professional 3D print shop said that he used mineral oil to get rid of sanding marks on prints as it was one of the best ways to do it.

Another user said that Vaseline works wonders in fixing PLA that has turned white after sanding.

Several users said mineral oil was an effective method of removing the white color after sanding PLA. Some suggested using it as a final step after sanding with higher-grit sandpaper. They said you should take a rag, add mineral oil and rub it down the affected parts.

5. Use Clear Coat Spray or Clear Spray Varnish Lacquer

Some people in the 3D printing community have used clear coat spray to fix sanding PLA turning white with great results. Sanding PLA removes its top layer leaving an exposed surface that may appear white.

To fix this, you can apply a thin and even coat of Clear Coat spray or Clear Lacquer Spray over the sanded surface, creating a protective layer and making the surface more even. This will help to get rid of the white discoloration and enhance the color of the PLA.

Check out the Krylon K01305 Clear Coat Aerosol on Amazon.

One user wanted to know how he could fix PLA turning white after he wet sanding. Users said using a clear coat or spray varnish would do the trick. Someone recommended testing it first.

This could be done by making a tiny test print, sanding, and clear coating it allowing you to see how the print would turn out.

Another user said that to remove white marks that appear after sanding, he washed his print with a sponge to remove all the dust and left it to dry properly. He followed it up by applying a Clear Spray Varnish Lacquer, which caused the white to disappear.

6. Wipe with Acetone

Wiping the sanded PLA with Acetone to fix sanded PLA turning white has an almost similar effect as heat/flame polishing. This is because it slightly melts the PLA’s surface layer, allowing it to soften and smooth out as it cools. As a result, the white spots will disappear.

Before starting, wear the appropriate personal protective equipment (PPE), such as gloves, and ensure your workspace is well-ventilated. After that, dampen a clean cloth with a small amount of acetone and gently wipe the sanded PLA surface.

Although acetone doesn’t dissolve PLA, you should not apply it excessively or expose PLA for too long, as this can damage it.

One user said he used acetone to remove white spots that had just been sanded. He splashed a little on the cloth and wiped the sanded spots, restoring the original color. However, he advised against using acetone as a vapor. Here is a picture of his results.