Fish! Conserving fluid preserved specimens for display
Hanging the Swordfish
Hanging the Swordfish
Bonito (Sarda sarda)
Trigger Fish (Balistes carolinensis)
For October and November 2010 we have opened a small exhibition in our main hall celebrating the diversity of fish found around the UK. These fish are all from our collections, with the oldest specimens going back to 1904.
To get these specimens usable for display we have had to do some conservation work. This has been as simple as cleaning the glass jar or Perspex display tank, to working on the specimen itself and changing the preservation fluid. How the fish has been preserved can affect its overall appearance and condition, but unfortunately whatever method we use the colour will be lost.
Many of the fish have been preserved in an alcohol solution, usually ethanol, which does result in shrinkage and the fish becoming very stiff. The preserving fluid can also become a very dark amber colour. This is due to materials such as lipids in the fish tissue being extracted out by the alcohol solution. However we know ethanol based preserving solutions work as the practice has been going on since the 1600’s! In more recent years we have found that it can also preserve DNA that is usable in modern molecular studies.
Another common preservative is formaldehyde, commonly called formalin. A diluted solution, usually of around 4% formaldehyde, has been used for over a century now. Formaldehyde causes chemical cross linking reactions in the biological tissues and this is termed ‘fixation’. Unfortunately formaldehyde does have problems, being pungent and potentially toxic to work with.
Some of the fish have also been preserved in a fluid called ‘Steedmans’. This is a mixture of propylene glycol (often used in anti freeze), a phenol (an aromatic organic chemical) and formaldehyde. This can preserve fish shape very well but there are concerns over its long term preservation properties.
For the main hall display all the preserving fluids were checked. All the specimens in formaldehyde and ‘Steedmans’ were moved to a safer alternative. This uses a chemical called DMDM Hydantoin which replaces the use of formaldehyde in everyday products such as shampoos and cosmetics and is much safer to work with.
Some of the specimens themselves needed some cleaning and tidying up. After years in a jar many had a build up of old proteins and fats on their surface. Other specimens had corrosion products on them from old metal tags that had been used for labels. Many of the specimens were also moved to more suitable glass jars.
The end result is an intriguing display highlighting specimens with fishy stories from the museums collections. The aim has been to make the specimens as accessible as possible so that visitors can get a close look at the preserved fish. The exhibition also represents the ongoing work that is required to care for the museums natural history collections for both now and the future.
Opening up the Collections
Final Natural History Open day – Wednesday 27th October 2010
Members of the public will be given an intimate insight into the museum’s natural history collections next week. As part of the International Year of Biodiversity, the departments of Biodiversity and Systematic Biology along with Geology have been holding open days throughout the year to showcase the work that they do.
Museum experts in a wide range of fields, from bugs to beetles, dandelions to diatoms can all be found in the main hall along with a crazy array of critters from the national collections. Visitors can also sign up for a wide variety of behind the scenes tours where they will be able to find out more about the incredible collections that the museum holds and the research that we do.
I will be running tours of the large shell collection, showcasing some of the 2 million shell specimens that we hold as well as explaining some of the work that is carried out by our researchers. Other tours will take you round the Welsh National Herbarium, the amazing vertebrate collections with their primate skeletons and stuffed animals, the insect collections with butterfly specimens over a hundred years old, and the vast array of pickled animals in jars in our marine lab.
This is to be the final open day for this year, so don’t miss your chance! Come and meet the experts and take the opportunity for a unique trip behind the scenes. Book your tour place on the day - numbers are limited to 10-12 people on each tour. Tours are suitable for ages 8 and over, but unfortunately are unsuitable for people with limited mobility because of the stairs involved.