A customer (Mark) who has much experience with FUD and FXD products recently sent me this message: "I moved from Wisconsin to Arizona in July. My stuff sat in a warehouse for about 3 months. When I unpacked my Pennsylvania stuff [3D-printed models for the battleship USS Pennsylvania] I noticed that the 3D printed stuff had formed a light crystal like surface. I managed to brush a lot of it off and with light airbrushing I should be able to cover almost all if it. I did clean the stuff pretty good and let it cure. Have you had any experience with this?" I have not heard of this happening before. Do any of you have any thoughts about crystals forming on top of paint some time after painting? Here's the advice I provide to customers with each product description and Mark has followed this advice to good effect on other products in the past without any crystalline surface problems occurring: "Some part cleanup will be necessary. During the 3D printing process, a waxy substance is used to support certain part features. Although the parts are cleaned by Shapeways afterwards, some waxy residue may remain. It can be safely removed with water and a mild aqueous detergent like “Dawn” dishwashing detergent, baby shampoo (no conditioner) or "Simple Green" using an old, soft toothbrush, Q-tips or pipe cleaners. During the printing process, liquid resin is cured by ultraviolet light. Microscopic bits of resin may remain uncured. Let your parts sit in direct sunlight for a few hours to fully cure the resin before painting. Once your parts are fully cured, if desired, careful use of an inexpensive “air eraser” emitting common household baking soda can help smooth surfaces and remove any unwanted “frost”. Similar to an airbrush but much cheaper, air erasers can be found on Amazon.com. Models by Harbor Freight and Paasche are popular. Water-based acrylic paints meant for plastics is strongly recommended. Other paints, especially enamels, may not cure on Frosted Detail 3D-printed plastics."* *Some forms of liquid resin naturally harden very quickly. To keep those resins in a liquid state so that they can extruded by a 3D printer, a chemical inhibitor is added to the resin at the factory. UV light destroys the inhibitor allowing the resin to naturally harden. The inhibitor can also prevent enamel paint from hardening. Post-curing the model by exposing it to UV light before painting can prevent problems with enamel paints.