Hi Mike & Adam,

A late reply (just scrolling through a backlog of listserv emails) but I'll add that my experience is similar to Adam's. Some paper gets quite delicate in propylene glycol over time - even with field-written labels. When written in pencil, they can become difficult to read as a result, not helped by the fact that PG tends to turn paper translucent. Soaking the labels in ethanol seems to help with sturdiness, but labels never fully regain their opacity in my experience.


On Fri, 7 Dec 2018 at 21:15, ahaberski <[log in to unmask]> wrote:
Thanks for this Mike,

I collect all of my samples into 100% propylene glycol with printed labels (same printer/ink/paper we use for specimen labels). After ~6 months the labels have become delicate, and a little over handling turns them to mush. It might be worthwhile to do a paper test. 


On Fri, Dec 7, 2018 at 12:06 PM Mike Ferro <[log in to unmask]> wrote:
I’ve been a proponent of using (or at least seriously studying) propylene glycol instead of alcohol for collecting, for shipping, and for long term storage of insect specimens. I’ve always thought about it from the standpoint of the specimen (internal/external morphology, color, DNA), but not the label. Victoria Bayless asked me about how propylene glycol interacts with ink, so I did a quick study. Maybe someone has done this in the literature already. 

I used 1) a pencil, 2) a Pigma pen, [three ball point pens] 3) black Bic, 4) blue free pen, 5) red Pilot, 6) black Sharpie. I used our standard label paper: HP Q6608A Glossy Laser Brochure Paper, White.

Treatments were as follow: 
1. Control, left dry.
2. immersed in 95% EtOH for 8 days, removed and air dried. 
3. immersed in 95% EtOH for 8 days, transferred to 100% propylene glycol for 8 days, removed and air dried.
4. immersed in 100% propylene glycol for 8 days, removed and air dried.
5. immersed in 100% propylene glycol for 8 days, transferred to 95% EtOH for 8 days, removed and air dried.

All the treatments basically reacted the same. Based on what I tested, if the ink is not dissolved in alcohol, it will not dissolve in propylene glycol (pencil and Pigma) and vice versa. The ball point pins aren’t too surprising because they often use propylene glycol as a solvent. 

If you do run across an instance of an ink that stood up to ethanol, but was dissolved by propylene glycol, please sing out and be heard! 





Michael L. Ferro
Collection Manager, Clemson University Arthropod Collection (CUAC)
Dept. of Plant and Environmental Sciences
277 Poole Agricultural Center
Clemson University, Clemson, SC 29634-0310
OFFICE: 307 Long Hall
Subject Editor: The Coleopterists Bulletin; Insecta Mundi

Spencer K. Monckton
Ph.D. Student
York University