Point mounts are my bread and butter. The wasps I study usually cannot be pinned—they’re too small—so we affix them to tiny triangles punched from archival card stock, skewered on a pin. The technique is pervasive, as the entomological collections community as a whole makes >400,000 such specimen preps annually. Check out this video from a collections master, Ed Riley of Texas A&M:
This is pretty much how I’ve done it, for 20 years. He uses Elmer’s Glue-All and clear nail polish, but, as hymenopterist tradition dictates, I preferred shellac or fish glue (Seccotine). Only recently have I started folding archival white glues (polyvinyl acetate or PVAc) into the process for certain insects.
A few weeks ago I wrote about how our use of these adhesives was questioned by a visiting museum conservation expert. The subsequent discussion inspired me to survey the entomology community for two main pieces of information: (1) What properties do we consider to be important for adhesives used in this context. Is there consensus? And (2) what adhesives do we use? With the results in hand, I dove into the polymer chemistry and museum conservation literature for information that would help me determine whether our chosen adhesives match our required properties.
A first draft of my review is now available:
Deans AR. (2018) A review of adhesives for entomotaxy. PeerJ Preprints 6: e27184v1 DOI: 10.7287/peerj.preprints.27184v1
As a community we pretty much agree on which adhesive properties are important, with the top three being: (1) archival, (2) reversible (many responded that this was equally important to “archival”), and (3) easy to use/prepare. We also appear to employ three main types of adhesives: (1) polyvinyl acetate (“white glue”), in various forms, (2) clear nail polish, and (3) shellac, with a few others types used less frequently.
My subsequent adhesive review, I have to admit, has thrown me into an existential crisis. All of our adhesives are critically flawed, and, if you trust the literature from other domains, we are generating hundreds of thousands of curatorial problems each year.
There are a lot of caveats, of course. The physics and chemistry at this small scale—a tiny dot of adhesive, securing cuticle to card—may be quite different from, say, coating the back of a canvas with a thick dollop of PVAc. And I certainly do not want to discount the vast experience of experts who have had to deal with point mounts and the real process of reversing them. We definitely need more rigorous research here, based on objective observations and data.
Given those caveats, however, I think I can comfortably make two solid recommendations:
- Stop using Elmer’s for point mounts! It is not archival, it doesn’t age well, it remains acidic, and the formula is proprietary and changes over time, sometimes radically. When I told a group of collections experts recently that most of my colleagues used Elmer’s for specimen mounts they audibly gasped and followed up with soft, awkward laughter and a lot of head shaking
- Stop using cellulose nitrate-based (“nitrocellulose”) clear nail polish for specimen repair and point mounts. Its aging properties are worse than Elmer’s, and these joints will ultimately fail (almost definitely within our lifetimes)
Other recommendations I am pretty sure will hold up upon further research:
- Stop using shellac for point mounts. Shellac bonds are very difficult to reverse, and the joints will become brittle with age
- Stop using PVAc (AYAF, AYAT, AYAC, Gelva, etc.) for these mounts. They age poorly, as poorly as Elmer’s, and will accumulate dust and debris over time
We’re doing more research, including some chemical analysis of other adhesives. Overall, though, I’d say I am disenchanted with this type of specimen prep. I might just move to minutens for some specimens or stick to ethanol. If you’re looking for an adhesive with proven long term archivability (but not easy reversibility) I’d look at this class:
- Poly(ethylene-vinyl acetate) (PEVA) coplymer, like Jade 403 or Evacon R.
They age well and are considered archival. Keep in mind, however, that these adhesives have a very short shelf life (six months) in the bottle. (This is true of any PVAc dispersion!) The set adhesive will also likely accumulate dust and debris over time and ultimately will be difficult to reverse. Another one worth experimenting with:
- Paraloid B-72 acrylic copolymer. It is a known archival material, with proven reversibility. You can buy it in prepared tubes or make your own, from beads dissolved in acetone or ethanol
We’ll have a lot more to say at the Entomological Collections Network meeting in November, including more on animal-derived adhesives (hide glue, etc.), Martha Stewart clear gel, gums, and others. Stay tuned!
Walter B. Sikora, Museum Associate, Georgia Museum of Natural History, Athens, GA says
Hallelujah ! I have just now (Feb. 9, 2024) found your Website titled “Point-mount disenchantment. I have thought about the problem of adhesive durability, archivability and reversibility in the future event that specimens may need to be un-glued for dissection etc.