Smoothing station (Polymaker Polysher)
An automatic smoothing station is a safest and fastest way to achieve a smooth, glossy surface on your prints. Simply put the model inside for 35-40 minutes and then let it dry for two hours. The main disadvantage is the high price of such stations.
15-30 minutes of washing in IPA bath
Immersing a 3D-printed PVB object in IPA can lead to a perfectly smooth surface. However, this method has several disadvantages you should take into consideration: The print usually floats (depends on its infill and other factors) and the surface becomes somewhat soft and “slimey”. This means that it’s difficult to remove the model from the bath without disrupting the smooth surface. Also, it takes a long time for the model to dry completely. The washing itself takes 15-30 minutes and drying takes usually several days.

Washing in IPA for short periods of time
A good-looking surface finish can be also achieved with consecutive shorter washing times. Disadvantages are similar to the longer exposition, however, by immersing the model in IPA for a short time, it melts only on the surface, while inside it remains solid. Simply immerse the model in an IPA bath for 30 seconds, remove it and let it dry for at least 15 minutes. Repeat this process five times or more for good-looking results.

Smoothing in IPA vapors
We’ve shown you this method in our older article. Its main advantage is low IPA consumption and easy solvent and model manipulation. But you should keep in mind that surface smoothing might be uneven without proper air circulation inside the box and it usually takes a long time (dozens of minutes to few hours). The process is simple: Pour a small amount of IPA inside the smoothing box, place the model on an elevated metal platform inside and wait. Check the model regularly to see whether it’s not melted too much. Keep the box warm and ensure good air circulation inside to get the best results possible.
If you don’t have any proper box and need to smooth small models, you can use an improvised method with kitchenware. Take a cylindrical glass, put a napkin soaked with IPA on the bottom and secure it properly. Printing a circular gadget with flexible filament might help. This will serve as a lid for your smoothing box. The bottom consists of a plate filled with water and an elevated (metal) platform in the middle. Put the model onto the elevated platform and put the glass onto it (bottom facing up). Let it work for 2-3 hours, however, don’t forget to check it regularly.
Spraying IPA directly onto the surface
This is basically the same method used in Polymaker Polysher. The main advantage is low IPA consumption, disadvantage comes with applying too much or too low IPA that might lead to uneven surface finish. IPA application and drying (at least 10 minutes) should be done at least five times.

Using a regular brush
This is by far the simplest method you can use. However, it comes with three main disadvantages: Using the brush usually takes a long time, the brush can leave marks on the surface, and with the incorrect application, it may even leave bristles on the model. If you choose this method, apply IPA onto the model’s surface, then let the model dry for at least 30 minutes. Repeat if needed.