6 Ways How to Polish PLA 3D Prints – Smooth, Shiny, Glossy Finish

PLA is the most popular 3D printing material, so people wonder how they can polish their 3D prints to make them smooth, shiny, and give them a glossy finish. This article will take you through the steps to make your PLA prints look great.

Keep on reading for more information about making PLA prints polished and shiny.

How to Make PLA 3D Prints Shiny & Smooth

Here’s how to make PLA 3D prints shiny & smooth:

1. Sanding your Model
2. Using Filler Primer
3. Spraying Polyurethane
4. Applying Glazing Putty or Airbrushing it
5. Using UV Resin
6. Using Rub ‘n Buff

1. Sanding your Model

One of the most important steps to make your PLA 3D prints shiny, smooth and looking as good as they possibly can is to sand your model. Sanding can be a lot of work but it’s worth the effort as it will hide the layer lines making it a lot better to paint and apply other finishing touches.

For that, you can use sandpapers of different grits, like the PAXCOO 42 Pcs Sandpaper Assortment from Amazon, ranging from 120-3,000 grit.

It’s a good idea to move from a low grit sandpaper, then more to finer grits as you progress.

One user recommended doing the following:

• Start with 120 grit sandpaper and sand your pieces
• Move up to 200 grit
• Then give it a finer sand with 300 grit sandpaper

You can move up to a higher grit depending on how smooth and polished you want your 3D print to be. It’s always good to have a wide variety of grits, going from course to smooth, and you can even do dry or wet sanding.

Even when you plan on using other methods to smooth and polish your PLA 3D prints, you still want to sand it first.

Here’s a great example of some successful sanding of a PLA model.

If you are getting small white grooves on your PLA print after sanding, try heating them a bit with a lighter or heat gun to get rid of them. Make sure you don’t heat up the model too much or it can quickly deform, especially if the model’s walls are thin.

You can use something like the SEEKONE Heat Gun from Amazon. One user said using a heat gun is great for restoring the original color of PLA after sanding since it can get discolored easily.

If you gradually move up in sandpaper grit, that can also get rid of the white marks on your PLA.

Darkwing dad has a great video on YouTube about how to properly sand PLA printed parts, check it out below:

2. Using Filler Primer

Another great option to get your PLA prints smooth and glossy is using filler primer to smooth out the imperfections of your 3D print. Filler primer can help hiding layer lines as well as making sanding a lot easier.

There are a few different options of filler primer to choose but one of the most recommended for PLA 3D prints is automotive filler primer, such as Rust-Oleum Automotive 2-in-1 Filler, available on Amazon with great reviews.

One user started to use Rust-Oleum filler primer on his PLA pieces and found that they got a lot smoother, offering a better end-product.

Another user found that 90% of his layer lines disappeared when spraying filler primer on the printed object besides also cutting down on sanding time. Just be careful not to lose too much dimensional accuracy by using too much filler if that’s something you want.

Many people have been impressed with the results achieved after sanding and using filler primer on PLA objects because it allows for a very smooth and polished surface, perfect for painting afterwards.

Using a good filler is a great way to cover up imperfections and layer lines on a 3D print.

A user that has gotten good results recommended following these steps:

• Sand with low grit sandpaper like 120
• Assemble any pieces if needed
• Use filler putty in big gaps – spread a thin layer over the whole model
• Let it dry then sand with 200 grit sandpaper
• Use some filler primer and sand again with 200-300 grit sandpaper
• Paint if desired
• Apply a clear coat

FlukeyLukey has an awesome video on YouTube about spraying automotive filler primer to smooth your PLA 3D print, check it out below.

3. Spraying Polyurethane

If you’re looking to leave your PLA prints smooth and shiny then you should consider the method of spraying polyurethane on the printed model as it is thick enough and dries fast enough to fill in the layer lines, helping to create a better look to the finished object.

I’d recommend going with something like the Minwax Fast Drying Polyurethane Spray from Amazon. It’s a popular choice with the 3D printing community for smoothing PLA prints to a polished finish.

Be careful not to apply too much polyurethane because it is really thick and can remove a lot of detail, as it happened to one user who was trying to smooth out a blue PLA print. He still thinks the polyurethane added a lot of shimmer to his object.

Another user really recommends using this Minwax Polyurethane Spray as it makes adding it much easier than using a brush, he suggests doing a couple of coats in satin, high-gloss or semi-gloss to really add some shine to your object.

He also thinks it is extremely useful for clear PLA as it removes the “haze” present on surfaces and allows the print to become really transparent.

Spraying polyurethane helps to seal PLA 3D prints and even slows down the process of absorbing moisture and degrading, making the models last longer. It’s great for waterproofing PLA prints, even one coat getting the job done.

Even food safe objects can be created by using a coat of food safe polyurethane.

3DSage has a really cool video about spraying polyurethane to help smooth out PLA prints that you can check below.

4. Applying Glazing Putty or Airbrushing It

There is another great method you can try in order to polish and properly smooth out your PLA 3D prints and make them as shiny as possible. It consists of airbrushing glazing putty on your object to help hide layer lines and give it a nice smooth finish.

You will need to reduce the glazing putty in acetone so be aware that you will need to take the adequate safety measures, using proper gloves and a mask/respirator to handle toxic materials.

If you don’t have an airbrush setup you can still use glazing putty normally and just not reduce it in acetone. The most popular glazing putty in the market seems to be Bondo Glazing and Spot Putty, which is available on Amazon with great reviews.

One user really likes Bondo Glazing and Spot Putty to smooth out his PLA prints, he doesn’t use the airbrush method, he just applies it normally but he does recommend you to sand the piece after applying the putty.

A reviewer said he uses this putty to fill in print lines on his 3D printed cosplay pieces. He mentioned that plenty of people recommend it and there are many video tutorials that show people how to use it. It’s easy to apply and sands easily.

It’s a good idea to sand the object before the putty fully dries out since it’s easier to sand before that.

Check out the video below by Darkwing Dad who shows you how to airbrush Bondo Putty on your 3D print.

5. Using UV Resin

Another method of smoothing and polishing your PLA 3D prints is to use UV resin.

It consists of applying standard clear 3D printer resin to the model like some Siraya Tech Clear Resin with a brush then curing it with a UV light.

When you do this method, you want to brush the resin along the layer lines to avoid creating bubbles. Also, you don’t want to dip your whole model in the resin since it’s not very thick and you don’t need to apply much of it.

It can be done with just one thin coat, especially if you don’t want to decrease the detail in the model too much.

After the coat of resin is on, use a UV light and a rotating turntable to cure the model. It could be a good idea to tie some string to a part of the model so you can elevate it, then coat and cure it in one go.

You can use something like this Black Light UV Flashlight from Amazon. Many users have said they used it for their resin 3D prints to cure them.

Some users recommend that you pour some of the clear resin on a paper towel, then dry it on a UV light to use it as a curing time reference so you know how long to cure it for.

Using this technique can really get you a smooth polished surface and hide your layer lines in PLA models.

One user who has an Ender 3 said he achieved great results by filling out the layer lines and smoothing it out using the UV resin technique. He said the UV resin immediately got rid of the layer lines and help make sanding easier.

You can watch the video below by Panda Pros & Costumes on how to use the UV resin method.

6. Using Rub ‘n Buff

Rub ‘n Buff (Amazon) is one of the easiest options when making PLA prints smooth and shiny. It is a paste you can apply by rubbing it on the object’s surface to leave it more shiny and give it a unique look. Just remember to use rubber gloves to avoid any skin irritation.

It comes in a variety of different colors and metallic tones and it can give your object a unique finishing touch.

One user who put this product on their 3D prints said it worked great for making objects look like metallic silver. He uses it for post-processing 3D printed replicas successfully.

Another user said he uses it to add elegance to some lightsabers he 3D printed with black carbon fiber PLA. It works great and lasts a long time as one person put it. You can apply it with a small brush for better accuracy, then rub it with a clean cotton cloth.

Even a tiny blob of this stuff can cover large areas. Check out the example below of Rub ‘n Buff on black PLA.

Another user really liked how Rub ‘n Buff performed on PLA 3D printed objects. Even without any other finishing touch, the final result looked very shiny and smooth, being a perfect option for those that lack the painting abilities.

Check out this other example also.

Check out this awesome video about applying Rub ‘n Buff to your 3D printed parts.