Fun With Fluids: Days Three & Four

Yesterday was a slightly slower day than intended, but I did manage to finish preserving both the frog and lizard and get them into their final solution of 80% IMS, and then mounted the frog on his backplate. Which was an odd experience – I took textiles GCSE, but it did not prepare me for threading a frog! With a very large, curved needle and monofilament thread. He did look good when he was finished, despite still being a little crunchy – the rehydration process didn’t seem to have much effect on his appearance.


At the end of the day I managed to prep the jar and glass backplate for the harbour crabs, so that I had everything ready this morning to crack on with mounting them. Tying them to the backplate was a fairly quick job, but then came the harder task of reattaching the stray claws and legs with glass needles. I first had to decide which crab which limb belonged to, and then exactly where each limb should go. It took quite a long time, but I got there in the end!


There are still a few more limbs missing, but they weren’t in the jar with the specimens so must have been lost long ago. Once in their nice new jar, though, the crabs looked much happier.


Sadly, by the time I’d finished mounting the crabs, and had sealed the jars of my finished specimens, I didn’t have time to finish the lizard. I had the jar prepped, and all ten holes drilled in the backplate, but I didn’t have time to mount it. One of our conservators has offered to finish it for me tomorrow, and I left her with the worst diagram of a lizard ever drawn to show her how I had planned to pose the lizard, which I hope will help her to sew him to the backplate in the right position. He’ll probably end up looking much better than if I’d done it!

Poor little Varanus waits patiently for a new jar

Poor little Varanus waits patiently for a new jar

There has been a huge amount to take in this week, as there are so many different processes involved in restoring dried-out specimens, and I’m now quite exchausted. But I am really pleased with the results of my specimens, and I’ve learned a whole host of new skills that I feel confident I could put to good use in the future if someone put a shrivelled specimen in front of me.

If you have wet-preserved specimens in your collection that you don’t know what to do with, or don’t think you can rescue, I’d highly recommend going on Simon’s fluid preservation course – I was amazed at how well all of the specimens we worked on this week came out. They all started as dry, sad-looking husks, and by the end of the week most of them looked ready to go on display!

 Before: P1110830 P1110826

OLYMPUS DIGITAL CAMERAChameleon, octopus (named Little Chulhu) and sea slug, prepared by Gina

Fun With Fluids: Day Two

Today began with us checking our specimens in their baths of Decon-90. My harbour crabs were declared done and ready for fixation, but the tree frog was still rather stiff and unresponsive, so he went back on the hotplate to cook a little longer.

‘Fixing’ specimens involves bathing them in a fixative, in this case formalin (a dilute solution of formaldehyde dissolved in water), which stabilises tissues by binding to amines in protein, making them less soluble and mobile. Most specimens also need to be injected with formalin, to ensure that it penetrates the whole body and the internal organs don’t start to degrade. My crabs did not need injecting, as the formalin could get inside the carapace fairly easily to reach the tissues.


Here you can just about see the glass microscope slides being used to force my still floaty crabs beneath the surface of the formalin to make sure that it penetrates evenly.

While our specimens were busy fixing, we went for our morning’s lectures, which included information on the various jar sealants that have historically been used and which one is likely to come across in a museum collection, mounting pelagic specimens using monofilament wire and glass backing plates, and also information on dealing with fluid-preserved botanical specimens.

Next it was back to the lab, where my frog was finally supple enough to be fixed in formalin, and my crabs were ready for the next stage. Once fixed, specimens are usually then transferred into alcohol, which acts as a preservative and prevents them decaying over time. A solution of 70 – 80% Industrial Methylated Spirits (IMS) is used for this. But with specimens that have dried out completely in their jars (as mine had), they can’t be put straight into 80% IMS, as this would damage them. Instead, they need to be stepped up in gradual stages to 80%, starting with a low alcohol concentration.

But before my critters could go into their alcohol, they had to be treated for the air inside them that was causing them to float. This was done in a dessication chamber attached to a vacuum pump, which pulls the air out of the chamber, and removes air bubbles from the body cavity of the specimen.


Unfortunately, while quite a lot of air did come out of my specimens, they failed to sink totally, even after several treatments in the vacuum. As the frog will be mounted on a glass backing plate anyway, this isn’t too important.

While waiting for my specimens to work their way up the alcohol ladder, I also attempted to make a lid for the frog’s jar by cutting a circular piece of glass from a sheet…after three failed attempts, I resorted to a ready-cut lid! Which is cheating, but I did at least get the principle of how it should work, and why mine went wrong. I also drilled a hole in my shiny new lid, which can be used to top up the alcohol in the finished jar in the future if the level gets too low, without having to go to the hassle of removing the lid (which will be well sealed).

I also started a new project, which is this little chap:


He is a small monitor lizard (of the genus Varanus), and he has clearly been squashed into a jar that was too small for him, as he is rather hunched and his tail curls around quite a lot. His main problem, however, was that the fluid level in his jar was far too low, as you can see above. He was still fairly flexible, so I didn’t need to put him into Decon-90, but instead moved him into a nice, new, (and much larger) jar and doused him in his first batch of IMS.

Tomorrow I will finish moving the frog and the lizards up the alcohols, mount the frog on his backplate, and attempt to re-attach some stray crab legs. Can’t wait!

Fun With Fluids

So, this week I am attending an excellent course in fluid preservation of natural history specimens run by Simon Moore. Handily, it is also being held at the Horniman this time round, so I don’t even have to go out of my way!

Day one featured a morning of lectures on the various problems that face fluid preserved specimens, including drying out, lipid contamination, and incomplete fixation. There was a lot of information to take in, and a lot of chemistry involved – I haven’t studied organic chemistry since university so I’m a bit rusty, and I can’t say I took in all of the details of fixative formulae and chemical reactions! But the theory was followed by practical, which always makes things clearer.

The practical side of the course involves rehydrating some completely dried out specimens. The first step was to choose specimens – I managed to bag myself a small, rather mouldy tree frog (of the genus Rhacophorus), and a jar of three crabs (labelled as Portunus depurator, now called Liocarcinus depurator, the harbour crab).


My poor sad looking frog



A jar of dry crabs


The first step in rehydration is to bathe the specimens in a dilute solution of Decon-90 (which is usually used as a surface-active cleaning agent and radioactive decontaminant, but is also excellent for rehydrating dried tissues). I decanted the specimens from their jars into beakers, and placed them on hotplates to warm the Decon-90 solution slightly, which catalyses the reaction.



And in their baths they will stay overnight, as my specimens remain quite stiff and unreponsive so far. Tomorrow they will be treated in a mild vacuum to remove the air pockets that are causing them to float at the moment.

While waiting impatiently for our specimens to show signs of improvement, Simon showed us some techniques for glass cutting, which is important for making new lids for specimen jars, and also showed us how to drill holes in jars to top up fluids without having to remove the lid (which is often quite a chore if the jar has been well sealed).

Charlotte demonstrating how to drill holes in glass

Charlotte demonstrates how to drill holes in glass

By the end of the week I hope my little critters will look plump, healthy and lifelike again! I will keep you updated on progress…