MITRA Forum Question Details

​I have sent this to our framing housing expert.

“Archival” Coroplast is actually free of additives, while Coroplast is free of acid. They leave out UV inhibitors and anti-oxidants and colorants. There may still be slip or release agents, left on the surface, which means that it is not a material intended for contact with art. If you are drawing on plastic, keeping the acrylic away is likely to be a waste of effort, since static will draw the support sheet forward, in all likelihood. Using anything pressure-sensitive is going to cause problems. The drawings laid on a same size sheet of paper and sandwiched between the Coroplast and the glazing sheet, both of which should be slightly larger than the drawing. The edges of this sandwich can be taped with a good quality tape like 3M 850, or 450, after a strip of mylar has been placed between the edge of the package and the tape’s adhesive layer. to keep the sticky stuff at bay. Thought should be given as to how these packages will hang. One possibility is to make the Coroplast panels larger than the art, by a few inches and then score it to get the size that is just larger than the drawing. The board is bent open along the scores, after the corners have been cut, on the diagonal, so that they will not overlap at the corners. The outer portion can be folded in and taped flat and slits can be made, through the fold, where the hangers will be. Mylar strips can be threaded through those slits and taped into loops, where they are closest to the canter of the art, so that a hanging wire/twine can be secured to them. 

Hugh Phibbs.

​To echo part of Hugh's recommendation, I would steer clear of using any kind of tape directly on your art - even if it says "acid free" or "archival."  Those tend to be just as problematic as "regular" tape as they age.

I've used regular coroplast covered with Tyvek as a rigid transport surface for art and it worked well.

​I would still hesitate to use the Gudy adhesive, even if their website says it can be removed with glass cleaner or ethanol.  As tape ages, the adhesive becomes resistant to solvents and techniques that work when it is freshly applied.  I also would avoid applying glass cleaner anywehere near your art!  

I would also err towards using the archival Coroplast if possible; however, if you are pressed for time and the "regular" Coroplast is all that is available, I would simply use it only for display and store the Tyvek piece separate from the Coroplast (or with a buffering material in between) afterward.   

​Contact between acrylic sheet and art may be less consequential than contact between glass and art work. Glass is much harder than acrylic and glass is thermal reservoir, while acrylic is a thermal insulator, which means that when morning sun goes through glass, the glass stays cold, while the infra red in the sunlight warms the art and drives out moisture, which can condense on the cool glass. This is much less likely with acrylic, but acrylic can sustain a static charge more than glass can. Some media can be flattened by contact with either glazing sheet and if acrylic media sticks to acrylic sheet, it can pose a problem, since they will be chemically similar and must be parted physically. For that reason, spacing the acrylic sheet away from the art work described, here, is wise, but ensuring a complete absence of contact will be difficult to ensure. A spacer of Volara can be secured to the acrylic sheet with pressure sensitive adhesive, but static may pull the Tyvek forward and if 4 mil Coroplast is used, it will be flexible enough that it and the acrylic sheet may bend together near the center. The added expense of additive free, “archival” Coroplast is not needed and using a thicker version, 6, 8, 10 mil can make successful spacing easier to achieve.  If the art is to be held back, it will need adhesion to the support and while many water based adhesives can bond to flash spun polyethylene, Tyvek, they will not stick to the polypropylene of the Coroplast. The only safe adhesive that can be used for such hinging is Klucel G, hydroxy propyl cellulose, in a viscous form, (one part powder/one part solvent) since it has surfactant properties. It can be mixed with water or isopropyl alcohol, since all the bonding will be with plastic materials and it must be tested carefully, before being employed.

Hugh Phibbs, Preservation Specialist