by Lucy Treado, Spring 2015 Intern
During my internship at the Virtual Curation Laboratory, I have worked to prepare the 3-D printed artifacts made in the lab for educational purposes. A majority of my time was spent sanding and painting the printed objects. 3-D printing is an effective way to mass produce replicas of artifacts for educational purposes, however the replicas are not an exact match to the original object scanned. During printing, striation on the exterior surface occurs as the plastic is laid down in a uniform manner. In order to determine the most effective method of reducing the residual striations on the surface of the 3-D printed plastic artifacts, I have experimented with multiple forms of acrylic-friendly media applications on the printed objects to test their success at creating a smoother and more realistic surface area. Individual applications of gesso, self-leveling gel, and Flügger were applied to the artifacts prior to and sometimes after the acrylic paint was applied. I then compared the results of each application to the artifacts that received no other medium other than acrylic paint.
Applications of ProArt Premium Gesso Canvas Primer alone were determined to be unsuccessful for two reasons: first, a single thin layer of gesso resulted in no clear difference than simply using acrylic paint. The second reason gesso was ineffective as a means to reduce striation is that if applied in multiple layers or applied in one thick layer, it becomes unmanageable and a majority of the details of the artifact replica are lost. However, at $12.99 per 16 fluid ounce, gesso is cheaper than acrylic paint, and if properly tinted, would more cost-effective than the underlying off-white acrylic Liquitex Basics base coat we currently use.
Applications of Golden Self Leveling Clear Gel provided a much smoother surface area although there are a few issues to contend with: first, averaging $16.59 per 16 fluid ounce container, self leveling gel is an expensive product for the Virtual Curation Laboratory and to successfully fill the striations it requires multiple applications. Second, similar to the gesso application, self leveling gel can also end up filling-in important details of the artifact. However, because the gel is clear both during the application process and after fully drying, one can easily differentiate between the striations and important details of the artifact. Details can then either be painted back on or the gel could also be cut with a razor blade to enhance details of the 3-D printed artifact if one was so inclined. The third issue of self leveling gel is that due to it’s slickness, acrylic paint has a harder time adhering to surface. This is not a big issue, but I did notice that if I was over-working wet paint, it was more likely to just roll off the replica. The fourth issue of the self leveling gel is that it has a high gloss finish if used as a top coat, and when dry, a sticky film remains. It is possible to remove the high gloss finish with a bit of light sanding or buffing, however this would result in opaqueness, therefore reducing its value as a clear top coat. I personally found that mixing the gel with paint created a semigloss stain that works well as a top coat and reduces the strange tacky texture a bit. This works well for recreating replicas to look like polished artifacts, certain stones and metals, as well as other wet-looking surfaces.
Applications of Flügger also came with a few difficulties. According to suppliers such as Talas, this medium works best on a painted surface rather than directly on the plastic replica. In my own experience, I could not get the medium to stick very well to the unpainted objects and then I had to deal with clumps of dried Flügger before painting. My experiments with the material after applying a base coat were more successful. Similar to gesso, Flügger is an opaque white substance and it was easy to lose the important details of the artifact. Second, averaging about $19.95 per 13.5 fluid ounces, Flügger is an expensive product and therefore would not be cost-effective for the lab. Third, possibly due to my methods of applying the medium to the replicas, I was forced to spend a good deal of time after the initial application re-sanding the object. Flügger can be thinned out with water, however thinner coats would require more time from students and I am not sure that would alleviate the second sanding required.
(Scroll over the images to see details on the type of base used)
All three mediums offered positive and negative results, making it difficult to determine which method and base coat would be the most effective for the lab. In my opinion, the artifact should determine the base coat— specific items calling for a slight to high gloss finish would be best served by the gel medium, while objects needing a flat matte finish would be best served by the Flügger. Gesso would also work fine as a matte finish, and can be mixed with paint to extend the life of the paints and to cut costs. However, in thin layers, gesso does not do much in the way of filling the replica crevices. If this is not a big concern, then I suggest gesso is the most beneficial for everyday purposes in the lab. I also believe that proper sanding plays a major role in the outcome of the final project. According to both researchers Yong He, Guang-Huai Xue, and Jian-Zhong Fu as well as the 3-D printing company Air Wolf, the easiest method for removing the striations is via a chemical vapor bath. Yong He et. al (2014) suggest that the use of acetone vapor works well to reduce what they refer to as the “staircase” appearance (the striations) within six minutes, however left for too long the acetone vapor will destroy the surface area (p.2-3). The Air Wolf (2015) website illustrates the effectiveness of the acetone vapor, however they do point out that this can also lead to loss of detail (https://airwolf3d.com/2015/04/01/35mm-nozzle-vs-50mm/. This method might be too risky for the lab, as it requires ample ventilation and the entire process is a bit of a fire hazard. However, this is a method that I would like to try in the future, perhaps in my own home.