Post Processing

Whether your object was printed using resin or filament, some finishes can only be achieved through post-processing.

Magnets

I like magnets, and I cannot lie.

For several models, I added cylindrical negative volumes in the slicer so that I could glue magnets into the finished print.

Remove strings

After a filament print, you may notice some stringing. You can remove it by quickly passing a lighter’s flame near the affected areas.

Be careful not to overheat the print or burn your fingers.

Sanding and Smoothing

If you want smooth prints, be prepared to spend some time sanding.

You will need several sheets of sandpaper with different grits. Start with a coarse grit (low number) and gradually move to finer grits (higher numbers).

For an even smoother finish, you can apply filler primer, sand again, and repeat the process before applying the final coat of paint using very fine sandpaper.

Rotary tools can speed up the process, but be careful not to damage the print by applying too much pressure or generating excessive heat.

Assembly and Glueing

You may decide to print a model in multiple parts for many reasons: avoiding supports, creating objects larger than your build volume, printing in multiple colours, or making painting easier.

Some models are designed for easy assembly, while others require a bit more creativity.

I mainly use super glue (cyanoacrylate) to bond parts together. I’ve found that it works very well with PLA and creates surprisingly strong joints.

If the surfaces are textured, I recommend lightly sanding them before gluing to improve the bond.

Some people also recommend the following methods, although I have not personally tried them:

• A plastic welder
• A 3D printing pen
• Plastic welding by melting parts together
• 3D Gloop

Filling

Before painting your model, you may want to fill imperfections using materials such as wood filler, modelling putty, or filler primer.

Painting

Start by applying a primer so that the paint adheres properly to the surface. I recommend wearing a mask and gloves for this step.

You can then paint the model with acrylic paints. I personally use miniature-painting brands such as Citadel, The Army Painter, and Vallejo.

Varnishing

To protect your paint job over time, apply a matte, satin, or gloss varnish. I recommend wearing a mask and gloves for this step.

Water Tightness

Resin prints are generally more watertight than filament prints, but achieving a fully watertight FDM print can be challenging.

I have read a lot of advice on the subject: increasing the number of walls, increasing extrusion, using thicker layers, increasing infill, printing with PETG, applying acrylic coatings, and more. While some of these methods worked for a few days or even a couple of months, my prints eventually started leaking.

After many failed attempts, I started using epoxy resin. My epoxy-coated prints have remained watertight for over a year with no issues so far.

To do this, mix the epoxy resin according to the manufacturer’s instructions, apply a thin coat to the print, and allow it to cure completely.

It can be a bit messy, but I have found it to be inexpensive and effective.

I recommend wearing a mask and gloves for this step.

Food Safety

In June 2026, Bambu Lab released a new filament called PLA Pure. According to the manufacturer, all of its ingredients comply with EU 10/2011, the European regulation governing plastics intended for food contact.

Using a food-contact-compliant filament is one thing, producing a food-safe printed object is another.

To reduce contamination risks, many makers recommend using a dedicated printer, avoiding materials of unknown composition, and using a stainless steel nozzle instead of a brass one. Proper cleaning procedures and avoiding excessive heat that could degrade the plastic are also important considerations.

I recommend reading more on the subject before replacing kitchen utensils with 3D-printed alternatives.

For my own projects, I have used food-safe epoxy resin to fully coat prints intended for aquarium use. In general, I do not consider untreated FDM prints to be food-safe.

Vapor smoothing

Some makers print with ABS and use acetone vapour smoothing to create a glossy, nearly layer-free surface. You can find many tutorials online, such as this one from Formlabs.

I have not personally needed this technique, but it is worth mentioning.

Metal plating

You can add a real metal coating to a printed object through electroplating.

The process requires several materials and can be fairly time-consuming. Typically, you first smooth the print, apply a conductive coating, immerse it in an electrolyte solution, and use an electrical current to deposit metal onto the surface.

The resulting metal layer can then be polished to achieve a shiny finish.

HEN3DRIK created a great video on the subject.

I have not yet tried this technique, but I intend to experiment with it in the future.