Getting smooth PLA is the desire for many users, including myself, so I wondered, what is the best way to smooth/dissolve PLA filament 3D prints?
The best way to smooth or dissolve PLA is to use ethyl acetate as it has been proven to work well, but it is potentially carcinogenic and teratogenic, and also absorbs through the skin fairly easily. Acetone has been tested by some with mixed results. The purer the PLA, the less acetone will work to smooth.
Keep on reading to get the details behind dissolving your PLA filament and making it a lot smoother than just after coming off the print bed.
What Solvent Will Dissolve or Smooth PLA Plastic Filament?
Well, it’s quite simple, PLA plastic filaments when processed can come with some imperfections and manufacturing layers. Smoothening the finished product will prevent those imperfections from ruining the finished work.
One solvent that has gained recognition for dissolving PLA filament is DCM (Dichloromethane). It is a colorless liquid with a sweet smell. Although DCM does not mix well with water, it well with many other organic solvents.
It is an instant solvent for PLA and PLA+. Once the liquid evaporates from the surface of the PLA, a seamless and clean print is exposed.
However, due to its volatility, DCM is not so popular among printers who work with 3D. It may damage the skin if exposed, and it can also damage plastics, epoxies, even paintings and coatings, so you definitely want to take precautions when using it.
It is also fairly toxic, so you should wear protective clothing if you decide to try it out.
Acetone is also sometimes used to dissolve PLA. Generally, PLA in its pure form does not react to acetone. This means that unless the PLA is blended with another type of plastic, it cannot be smoothened by acetone.
This does not mean that acetone will still not work great on PLA if it is mixed. What can help is modifying the PLA by adding additives that the acetone can bond with.
This will help the acetone bond better and of course won’t reduce the overall appearance of the 3D print.
Tetrahydrofuran also known as oxolane may also be used in dissolving PLA completely. Just like DCM, It is however very dangerous and not recommended for residential use.
A great option to try out when trying to smoothen your PLA print is Ethyl acetate. It is primarily a solvent and a diluent. Ethyl acetate is a preferred option to both DCM and acetone because of its low toxicity, cheapness, and good odor.
It is commonly used in nail vanish removers, perfumes, confectionary, decaffeinating coffee beans and tea leaves. The fact that Ethyl acetate is easily evaporated also makes it such a great option.
Once the PLA has been properly cleaned, it evaporated into the air.
Caustic soda has been mentioned to smooth PLA as an affordable and available option. Caustic soda, otherwise known as sodium hydroxide can break PLA down, but won’t properly dissolve PLA unless it has enough time and agitation.
It would hydrolyze the PLA rather than smoothing it, so most likely won’t get the job done.
It acts as a sodium hydroxide base and helps to break down PLA. However, like most of the solvents mentioned above, it is also very toxic and harmful to the body.
Does PLA Dissolve in Acetone, Bleach, or Isopropyl Alcohol?
Although many people make use of Acetone, bleach or even isopropyl alcohol when trying to dissolve PLA, these chemicals are not 100% effective. Acetone for one makes PLA softer but also stickier leading to a residue buildup when the dissolving is done.
If you want to weld two surfaces together, then you can make use of acetone but if total dissolving is what you had in mind, then you can try other types of solvents.
For isopropyl alcohol, not all PLA will dissolve in this solvent. There are specially manufactured PLA from the Polymaker brand which can in dissolved isopropyl alcohol. Before trying it out, you should consider the kind of PLA being printed.
How to Smooth PLA 3D Prints Properly without Sanding
Many times, sanding is the preferred method of smoothing PLA due to the fact that many dissolving agents are either toxic, unavailable or harmful to the body. A method to try out if you do not want to sand or dissolve using chemicals is heat smoothing.
This works by heating the PLA print with fairly high levels of heat for a short time.
While this method has proven to be effective at smoothing, the downside is that more often than not, the heat is unevenly distributed around the print causing some parts to become overheated while some are under heated.
The overheated parts may melt or bubble and the model destroyed.
A heat gun is very ideal and may solve the problem mentioned above.
With it, the PLA filament heats up in less time and more evenly too. With this heat gun, you can have a smother PLA print. Many people have tried to use naked flame for PLA smoothing, but the result is always a damaged or color-changed print.
A heat gun is more ideal because the temperature can be controlled according to the smoothing needs of the print. The trick with heat guns is to melt just the surface and allow it to cool.
Do not let the print melt enough such that the inner structure begins to sag as this can damage the print.
A great heat gun that many 3D printer users go with is the Wagner Spraytech HT1000 Heat Gun from Amazon. It has 2 temperature settings at 750ᵒF and 1,000ᵒF, along with two fan speeds to have more control over your usage.
On top of 3D printing uses such as for cleaning up discoloration on prints, instantly melting stringing, and being used to heat smooth objects, it has many other uses such as loosening rusted bolts, thawing frozen pipes, shrink wrap, removing paint, and more.
Something else that works great on smoothing PLA is Epoxy resins. These are compounds used to manufacture paints, coatings and primers.
Their success in PLA smoothing boils down to the fact that they have the ability to seal PLA prints either porous or semi porous. To get a perfect finish, many 3D printing enthusiasts add sanding to the process.
However, if done well, epoxy resin coatings can still give a great final result. To use, make sure the PLA print is cooled, and warm the epoxy resin liquid until it is viscous enough to work with.
I wrote some more detail about this process in this article How to Finish & Smooth 3D Printed Parts: PLA and ABS.
This is to ensure that both the print and the epoxy resin are as smooth as they can be before starting the process. Soak the print in the epoxy resin and ensure that it is fully soaked before taking it out.
Let it dry out, and you should have a smooth PLA print.
The usual choice for smoothing your 3D prints without sanding is the XTC-3D High Performance Coating from Amazon. It’s compatible with filament and resin 3D prints.
This coating works by filling in those gaps, cracks, and unwanted seams in your 3D prints, then gives it a lovely glossy shine after drying. You’ll be amazed at just how well this works, and why you may have never heard of it before!
In conclusion, there are many methods of dissolving or smoothing PLA depending on the need and finishing required.
If you decide to try out any of the solvents, make sure you are properly protected as fumes from many of them can cause irritation to the nose, eyes and skin.
A combination of heat smoothing and epoxy resin coating are great methods to try out if you want a clean glossy PLA print without sanding.