Last week I was asked by a customer if it was possible to remove or strip acrylic paint from a 3D printed model. Knowing that some 3D printed plastics can be sensitive to chemicals this was not something that I had attempted but decided it was time I found out. In this post I will share with you what works.
You may be wondering why you would want to strip the paint? Well, there are several reasons but two of the most common are splattering caused by blockages in an air brush and paint being too thickly applied. Both can ruin the finish of a model.
With injection molded parts the paint can be removed with 91% alcohol or certain paint thinners. However even some of the stronger ones can remove detail from plastic parts. With 3D printed parts, particularly stuff printed in Shapeways’ Frosted Detail materials, these chemicals can have a disastrous effect as they react with the material causing it to melt or break up.
After doing some research I found a product called Dettol here in the UK which can safely be used to strip acrylic paint. Dettol, as pictured below, is a low price cleaner and disinfectant which can be watered down for cleaning tiled floors and work surfaces as well as cleaning minor cuts.
The primary chemical is chloroxylenol (C8H9ClO); the rest is pine oil, isopropanol, castor oil, soap and water.
In order to test this product I need something 3D printed which had been painted, and something that I would not be upset about if it turned in to a blob of plastic and paint. For over a year I have had one of my Yosemite Valley Railroad Log Cars sat on the work bench in a half-painted state. This car had been dropped and some of the detail parts had broken off so it was not high on my priority list. As you can see below it had received a total covering of the primary paint. The paint was an acrylic made by Revell.
As this is only a small model I found a small jar, filled it with Dettol and popped the car in.
Having read all sorts of suggestions about how long to leave the model in the Dettol I decided to be on the cautious side and only left it for two hours. I removed the car and already the paint was coming off on my fingers. I ran the model under the tap and gently rubbed the flat areas with my fingers and they almost went back to white.
For the underside with all the lumps and bumps I used a tooth-brush to gently scrub and this worked a treat.
At this point I stopped. I could have removed every last bit but I was simply trying to find a method that works. There is a drawback to doing this. The Dettol does have a temporary effect on the 3D printed parts. The car went very soft and pliable; it was very similar to when I heated this material with hot water to remove a bow. You can read more about that here. This softening did not last and once the part had dried it began to stiffen again. I don’t believe that it will remove any of the detail from the parts but if handled roughly in this pliable state the parts can easily be broken or torn if they are particularly thin. I left the car overnight and the next day it was back to being a hard model and was ready to receive paint, although there was a smell that took me back to falling over in the playground!
So if you reach the stage with your 3D printed model that there is nothing you can do to cover a bad paint job all is not lost and you don’t have to order a new shell. However I would still advise caution before dipping all your models in baths of Dettol; make sure you have a set down area ready for when the parts come out to reduce the risk of damage and avoid keeping the parts submerged any longer than necessary.
On another note should you wish to buy another 3D printed model, or even order your first 3D printed model, Shapeways are offering free shipping on any order untill the 12th of July 2015. Simply add your items to the cart and the free shipping discount is applied.