A limited range (in size, thickness and quality) of glass containers are available for mounting of museum specimens. It has always been a problem finding jars for smaller specimens like embryos and small bones. Large jars capable of accommodating specimen like the entire thorax or abdomen is also hard to find. The availability of a range of acrylic sheets together with their versatility in usage make it an ideal choice for making museum jars. The proposed technique is a modification of the method of Edwards and Edwards (1959) and has been successfully tried out and tested to satisfaction at the dept. of anatomy, St. John’s Medical College, Bangalore.
The equipment needed are a bunsen burner, L angle, autopsy saw, drilling machine with small drill bits, a smooth flat file, bench grinder, buffing machine and three mm thich cast acrylic sheets (brand Lucitel – reg trademark of EI Dupont De Nemours and Co, Wilmington DE 10698).
The specimen is measured in length, breadth and depth. It is fixed to an acrylic sheet (in which holes are made with a drilling machine) with a nylon thread. The sheet may be transparent or of a contrasting colour and serves as a background sheet.
In this procedure, the front, top and back of the jar are made from one continuous length of transparent acrylic sheet (referred to as the main piece in the discussion that follows). The acrylic sheet is marked and cut (using an autopsy saw) with quarter inch more than the specimen measurement in each of the three dimensions. The sheet is heated over a bunsen flame to facilitate easy bending. The sheet is bent using the L angle as the guide to the required degree to suit the specimen . The bend may be V or U shaped or any artistically suitable shape. Grinding is done at the cut edges with a grinding machine. For the sides and base plate of the jar, separate acrylic pieces are cut from the acrylic sheet with adequate margins for the trimming. A small hole is made in the corner of the base plate with a drilling machine to enable the jar to be filled with formalin.
Acrylic cement is prepared by dissolving 15 grams of acrylic powder in 100 ml of chloroform and stored in empty aluminium or polythene tubes. The prepared cement is run over the edges of the main piece. One side plate is placed on this edge and kept apposed for ten minutes – a light weight can be placed for this. The other side is also treated similarly and the second side plate is attached.
The bottom edge of the jar is neatly trimmed on the grinding machine. This is necessary to to provide an even edge for fixing the base plate. The jar now has a cavity into which the specimen can be kept in position. The cement is run over the bottom edge of the jar. Keeping the jar inverted, the base plate is pressed firmly on to the bottom edge of the jar and retained in this position till the cement sets.
Appropriate supports may be required to hold the jar inverted during the ten minute period required for the cement to cure. This can also be held manually provided hand shake is kept to the minimum. 10% filtered formalin (BDH – AR) solution is filled with the help of a 50 ml syringe through the hole in the base plate. Care is taken to avoid air bubbles. A small plug of perspex is forced with the acrylic cement into the hole in the base plate and snapped off level with the surface. All the sides plate edges are trimmed and filed with a smooth flat file followed by polishing with a buffing machine. The finished specimen is now ready to be displayed as a museum exhibit.
This method is economical, convenient and the jars can be prepared in the department to accommodate specimen of various size and shape. The equipment required is minimal. A single sheet is bent under heat to cover a greater area of the jar thereby reducing the number of joints. The bending must be rapidly executed. Also the heat must be adequate while bending as otherwise it leads to breakage of the acrylic sheet. Excess heat causes air bubbles to be trapped in the acrylic sheet. A few trials with scrap sheets is helpful. The procedure does not require any electrical heating equipment. No clamps are needed to retain the pieces as the cement cures rapidly. Since no grooves are cut ( no milling machine required), thin sheets (3 mm) can be used in this technique. The cement can be prepared locally using acrylic powder obtained during grinding. We have found this to be a reliable glue – no leakage in the last 30 years of its use. The jars are allowed to set in daylight and at room temperature. There is no evaporation of formalin if the jar is sealed airtight. It is desirable to keep the acrylic jar away from sunlight.