A word of caution when using Mylar/polyester bags to store sketches

[earl]

As I think most of us are aware, Mylar (polyester) bags are not recommended for cel storage. Despite their many advantages over polypropylene and polyethylene bags, their big downside is that cel paint will easily stick to Mylar. However, it is often recommended to use Mylar for sketch storage. The longevity, stability, strength, and clarity of polyester is highly desirable. All that said... Mylar has one big disadvantage (related to sketches) that I have seen mentioned, but not often thoroughly discussed in animation art collecting communities... static cling. The static generated by Mylar can, over time, lift graphite (and similar, friable materials like pastel) off of the paper. This can cause the artwork to fade, or worse, become smudged as it moves within the sleeve. Below is a picture of a polyester sleeve I recently removed a heavily shaded, graphite storyboard sketch from. You can see where the graphite has clung to the polyester on the inside of the sleeve.

graphite_mylar.jpg (177.02 KiB) Viewed 1374 times

After speaking with a group of archivists, they recommended using glassine to protect sketches. Glassine is (relatively) inexpensive and has been used by artists/archivists/etc to protect artwork for quite a long time. Graphite will not stick to it and it does not generate any kind of static. Also, while it is not as perfectly transparent as Mylar, it can be seen though.

All that said, I'm still using Mylar sleeves for sketch storage. But, in addition to the archival backing board and MC paper I place in each sleeve with my sketches, I'm now also including a sheet of glassine on top of the sketch so that it does not come into direct contact with the polyester. Additionally, I'm using glassine as interleaving material between each sketch of a cut within a single sleeve. This may be overkill for most people... but I'm a bit over-the-top when it comes to protecting my art. (I've included an image below of a piece with a glassine sheet on top of it, all within a Mylar sleeve, to show how easily the glassine can be seen through. I purchased mine here: https://www.clearbags.com/spec/glassine-sheets)

sketch_under_glassine.jpg (618.94 KiB) Viewed 1374 times

[tarakatsuki]

As I think most of us are aware, Mylar (polyester) bags are not recommended for cel storage. Despite their many advantages over polypropylene and polyethylene bags, their big downside is that cel paint will easily stick to Mylar. However, it is often recommended to use Mylar for sketch storage. The longevity, stability, strength, and clarity of polyester is highly desirable. All that said... Mylar has one big disadvantage (related to sketches) that I have seen mentioned, but not often thoroughly discussed in animation art collecting communities... static cling. The static generated by Mylar can, over time, lift graphite (and similar, friable materials like pastel) off of the paper. This can cause the artwork to fade, or worse, become smudged as it moves within the sleeve. Below is a picture of a polyester sleeve I recently removed a heavily shaded, graphite storyboard sketch from. You can see where the graphite has clung to the polyester on the inside of the sleeve.

graphite_mylar.jpg

After speaking with a group of archivists, they recommended using glassine to protect sketches. Glassine is (relatively) inexpensive and has been used by artists/archivists/etc to protect artwork for quite a long time. Graphite will not stick to it and it does not generate any kind of static. Also, while it is not as perfectly transparent as Mylar, it can be seen though.

All that said, I'm still using Mylar sleeves for sketch storage. But, in addition to the archival backing board and MC paper I place in each sleeve with my sketches, I'm now also including a sheet of glassine on top of the sketch so that it does not come into direct contact with the polyester. Additionally, I'm using glassine as interleaving material between each sketch of a cut within a single sleeve. This may be overkill for most people... but I'm a bit over-the-top when it comes to protecting my art. (I've included an image below of a piece with a glassine sheet on top of it, all within a Mylar sleeve, to show how easily the glassine can be seen through. I purchased mine here: https://www.clearbags.com/spec/glassine-sheets)

sketch_under_glassine.jpg

Good to know, I may have some sketches in Mylar bags as they were bought that way. What is the downside of using polypropylene bags for sketches? Most of mine are in those.

[earl]

Good to know, I may have some sketches in Mylar bags as they were bought that way. What is the downside of using polypropylene bags for sketches? Most of mine are in those.

I believe there is still a (much smaller) risk of static cling with polypropylene. Also, polypropylene is a less stable material than Mylar/polyester. It will degrade over time and need to be replaced (comic collectors deal with this all the time). Polyester is also a stronger material at similar thicknesses and less likely to tear. If you don't mind changing them out every 5-10 years, polypro bags are much cheaper. But, Mylar/polyester sleeves will likely never need to be replaced (or at least not for a very long time).