Project #1 à Embedding a dry opaque specimen

• We will take a small dried starfish as an example. Dry specimens give best results when "wet" with Bio-Plastic. Soaking in uncatalyzed Bio-Plastic removes air bubbles from the surface and air pockets from inside the specimen. Immerse the starfish, upside down, in uncatalyzed Bio-Plastic, using a small disposable container such as a paper cup of suitable size. Use 30 to 50 c.c. of Bio-Plastic to cover the specimen. If the specimen floats, it must be weighted down; a 1in diameter metal washer is excellent for the purpose. Note that minute air bubbles rise to the surface as the specimen is impregnated. Cover the container with a sheet of paper to keep dust out, and leave overnight.
• The next day select a small glass or metal container to use a mold. The finished Bio-Plastic cast will be exactly the same size. If using different pieces to create a mold, assemble it according to the directions and use rubber bands to hold the ends in place.
• Apple mold release compound to the inside surfaces of the mold with a camel’s hair brush. Mold release comes as a thin paste and dries quickly when applied to the mold surface. If using a take-apart mold apply the compound particularly to the cracks where the ends of the mold meet the main section. This makes the mold leakproof when liquid Bio-Plastic is poured into the mold. Don’t disturb the mold after the mold release has been applied.
• Pour 15 c.c. of Bio-Plastic into another disposable container. Add 12 drops of catalyst and stir with a glass rod. Stir evenly and thoroughly for about a minute being careful not to stir in bubbles. Pour the mixture into the mold and cover the mold with a piece of folded paper, to form a "tent" over it. Set the mold aside to gel overnight.
• After the layer has gelled, about two hours, to the point where it no longer flows, it is ready to support the specimen to be embedded. With forceps, lift the starfish from the plastic in which it has been soaking and drain off the excess. Place the specimen on a paper towel or blotter. After draining for 10 minutes, move the starfish about on the towel or blotter until most of the liquid plastic has been removed. Now position the starfish upside down in the mold on the supporting layer that you have prepared. In two hours the specimen will adhere firmly to the supporting layer. This is very important where specimens have a tendency to float; you don’t want the specimen to rise to the surface when you pour the second layer.
• After the two-hour period put 30 c.c. of Bio-Plastic into the same container in which you mixed the first layer. Add 12 drops of catalyst and stir thoroughly. Pour the mixture into the mold, flowing it over the specimen, to a height near the top of the mold. Don’t let the plastic overflow the sides of the mold. Again, cover with the paper "tent" to protect from dust, and set aside overnight.
• Place the mold with the gelled Bio-Plastic into a "light bulb oven". Such an oven is provided in the materials kit, but may be improvised from an empty oatmeal carton and an extension cord with socket. Cut a hole in the bottom of the carton large enough for the base of the light bulb. Holding the extension cord socket over the hole on the outside of the carton, screw a 40-60 watt light bulb into the socket from inside of the carton; it will thus be held in place. Vent the top on two additional places with holes about the size of a quarter coin. These holes are for ventilation. Invert the carton with the opposite (open) end over the mold, and turn on the light bulb to provide heat. Temperature inside the oven should be maintained at about 140oF. Cure the plastic in this manner for about 3 to 4 hrs. At the end of this time, turn off the bulb and allow to cool inside the oven until at room temperature. Take out of oven and remove from mold. It should come out easily, due to the mold release compound and some shrinkage of the Bio_plastic itself in the hardening.
• The cast is now ready to grind and polish. Lay a coarse sheet of emery paper (180 grit) on a smooth surface such as a piece of plate glass, an enameled kitchen table-top, a piece of tempered Masonite, etc. Wet the back of the sheet to make it adhere to the flat surface. Grind the surfaces of the Bio-Plastic cast against this emery with a forward and backward motion of the block. This should be done wet. Apply a puddle of water to the paper, and work in this puddle. Wet grinding eliminates dust, provides a more even cut, and allows you to work back and forth on the surface without ruffling the emery paper. Next move to an intermediate grade of emery paper and finally to a fine grade. Dip the block frequently in water to observe the degree of grind. The sloping side of the stationary basement-type washtub is an excellent surface to work against in grinding a Bio-Plastic block. You might try this if one of these tubs is convenient to your work area.
• After finishing with the fine emery paper move to a felt polishing board to which has been applied a quarter of a teaspoon of a liquid abrasive. Again, polish with a back-and-forth motion. You will notice the block is acquiring a finer and more transparent appearance. For the final polish, use another felt board, applying a similar amount of liquid polish. Always keep the two felt boards separate for abrasive and polish, respectively.
• The more effort expended in grinding thoroughly through the various grits, abrasives, and polishes, the better the final appearance of your cast. If there are deep scratches on some of the surfaces of your block, it may be that at one stage in your grinding you didn’t spend enough time. Go back through the operations and resurface.

Project #2 à Wet opaque specimen by the Glycerine Method

Fresh plant or animal material can’t be directly embedded in Bio-Plastic. Before embedding, the specimens must be fixed in some preservative. All such common preservatives (70% alcohol) contain water. Water and Bio-Plastic don’t’ mix, and water will cause the plastic to become cloudy. Replace the water with glycerine, not because glycerine is a good mixer with Bio-Plastic, but rather because it prevents the Bio-Plastic from penetrating the tissue. When Bio-Plastic penetrates it clears, making the tissue transparent. This undesired effect in mounting opaque specimens is prevented by the glycerine. Be careful to remove traces of glycerine from the surface of the specimen. This is the reason for the acetone wash and careful drying of the specimen in a soft absorbant cloth. The glycerine method is used for preparing gross sections of preserved organs and animals, and for small organs and animals where a presentation of external form is desired. Proceed according to the following schedule:

• Select the specimen carefully—a small fish is a typical example—choosing as perfect a specimen as possible, well-preserved, straight, and complete.
• Transfer the specimen from the preservative to a 30% solution of glycerine in water for a period of 24hrs. the transfer to a 50% and 75% glycerine solutions successively, leaving the specimen for 24 hrs in each. Finally, transfer to 100% glycerine, also for 24hrs.
• Prepare the supporting layer for the mold. In this project, a slightly larger mold will be required than in project #1. The supporting layer should be about 1/3 of the total capacity of the mold, or about 20 c.c. Prepare the mold with mold release compound like in project #1. Dispense 20c.c. of Bio-Plastic into a disposable container. Add 16 drops of catalyst; stir well and carefully. Pour into the mold and allow to gel for two hours.
• Using forceps, remove the specimen from the 100% glycerine, swish it around in acetone for a few seconds, then press it to a clean, dry cloth or facial tissue. This removes much of the glycerine from the specimen.
• Place the specimen in a small disposable container and cover with about 50c.c. of uncatalyzed Bio-Plastic. Let stand for 2 to 3 hrs. Remove the specimen and drain on a blotter or paper towel as for the starfish in project #1. Discard the Bio-Plastic as it is now contaminated with glycerine. Add fresh uncatalyzed Bio-Plastic to cover the specimen again for 2 to 3 hrs. drain of f the Bio-Plastic and repeat. (It is important to remove from the surface of the specimen as much glycerine as we can to prevent its "bleeding" into the Bio-Plastic during the embedding; three such treatments are about right. With excessive soaking in uncatalyzed Bio-Plastic, the plastic itself will begin to penetrate the specimen, and the specimen will begin to "clear".)
• Both the specimen and the mold will its supporting layer are now ready. Remove the specimen from its third "bath" in the uncatalyzed Bio-Plastic and position it on the supporting layer, to allow the specimen to anchor (adhere to the supporting layer) several hours. The second layer will consist of about 45c.c. of Bio_plastic with 18 drops of catalyst.
• Proceed with the curing, grinding, and polishing as in project #1.