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Embedding specimens in plastic - Protocol (by marie Therese Rush)

 

ZOO*402 ICHTHYOLOGY

stained specimens

PROTOCOL

for the technique of embedding specimens in plastic

Day 1

Step 1: Read and understand the Material Safety Data Sheets associated with each of the chemicals used in this procedure.

Use of rubber gloves, lab coat, and safety glasses is mandatory.


Step 2: On working mat, place the following: metal disposal dish; label to be used for specimen; specimen in 100% glycerin; paper towels; tweezers to handle specimen; paper tent (for protecting solution from dust contamination); nail to be used as pointed probe, bottle of Bio-Plastic.

Step 2a: Remove specimen from 100% glycerin and place on paper towels. Mop up as much glycerin as you are able to from the specimen.

Step 2b: Pour approximately 100ml of Bio-Plastic from the bottle to the metal disposal dish. Gently place the specimen and the label into this uncatalyzed plastic solution. Allow to remain in solution overnight. This prepares the specimen and prevents contamination by glycerin. Place the paper tent over the specimen and container to prevent contamination.

Step 3: On working mat, place the following: mold, beaker containing water, measuring cup or ruler/tape measure for measuring the cubic centimetre(s) of the mold, pen and paper.

Step 3a: Select the mold you will use for the specimen. Calculate the volume in cubic centimetres (cc) or measure the necessary millilitres (ml) required to fill the mold. [Recall: 1cc = 1ml.]

Step 4: On working mat, place the following: mold, mold releasing agent, paint brush, metal disposal dish; paper tent; straw or other object (if you wish to have a hole running through the plastic block); stir stick (nail); dropper (for catalyst); bottle of catalyst; bottle of Bio-Plastic; knowledge of the proper amount of Bio-Plastic and catalyst to use. See table below:

Table: Amount of chemicals required for preparing the liquid plastic.

 Type of Container

 Volume of Container

 Chemicals required (bioplastic + catalyst)

 Amount of chemical required for base layer

 Amount of chemical required for covering layer

 Pyrex glass dish  20cc or 20 ml

 Bio Plastic

Catalyst

 10 ml

8 drops

 10 ml

8 drops

 Pyrex glass dish, custard type  60cc or 60 ml

 Bio Plastic

Catalyst

 30 ml

24 drops

 30 ml

24 drops

 Metal cake tin  60cc or 60 ml

 Bio Plastic

Catalyst

 30 ml

24 drops

 30 ml

24 drops


Step 4a: With care, and using a paint brush, paint the mold releasing agent on the inside of the mold, taking particular attention to the corners. Do not move the mold.

Step 4b: Pour the required amount of Bio-Plastic into the metal disposal dish. Add the required drops of Catalyst. Stir carefully (to avoid incorporating bubbles) for 1 minute. Pour the catalyzed plastic into the mold. Note: if you wish a hole to be placed within the block of plastic, cut a section of straw and with your finger covering the free end, place the straw vertically into the poured plastic. Hold straw upright for approximately 2 minutes and then gently release your finger from the straw. Cover with paper tent. Let this set for at least 2 hours (or overnight).

Day 2

Step 5: On working mat, place the following: mold, metal disposal dish; paper tent; stir stick; dropper (for catalyst); bottle of catalyst; bottle of Bio-Plastic; specimen and label to be embedded; tweezers; pointed probe; paper towels.

Step 5a: Carefully place the specimen and label on paper towels to absorb excess uncatalyzed plastic. Transfer specimen and label to base layer of plastic in the mold. Arrange accordingly.

Step 5b: Pour the required amount of Bio-Plastic into the metal disposal dish. Add the required drops of Catalyst. Stir carefully (to avoid incorporating bubbles) for 1 minute. Pour the catalyzed plastic into the mold. Rearrange the label and specimen if required.

Step 5c: Place the mold under incandescent bulb [40-60 watt bulb; distance 7.5 - 12.5cm] for 3 - 5 hours to speed up the polymerization process (hardening action). Turn off the light and allow the mold to cool to room temperature. Place paper tent over mold in order to allow heat and vapour to escape and to prevent dust contamination.

Day 3

Step 6: Remove mold, follow procedure for cast polishing. On working tray, place the following: cast; coarse, intermediate grade and fine grade emery paper; pail of water; tray containing liquid abrasive; felt polishing boards.

Step 6a: Lay a coarse sheet of emery paper (180 grit) on the tray. Wet the back of the sheet to adhere it to the tray. Apply a puddle of water to the paper. Wet grinding eliminates dust, provides a more even cut and allows you to work back and forth on the surface without tearing the emery paper. Grind all surfaces of the cast against the paper with a forward and backward motion.

Step 6b: Repeat the above procedure with the intermediate grade of emery paper.

Step 6c: Repeat the above procedure with the fine grade of emery paper.

Note: Dip the cast frequently in water to observe the finish.

Step 7: Apply a small amount of liquid abrasive to a felt polishing board. Polish with a back and forth motion.

Step 7a: Repeat the procedure using another felt polishing board.

 


stained & cleared fish

* * * * * * * * * * * * * * * *

 

If you have comments or suggestions,

please email me (marie Thérèse Rush) at:mrush@uoguelph.ca

 

Surtout, la pédagogie, c'est la raison qu'on crée des programmes!

 

Created: February 23, 2000

Updated: April 25, 2000

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