Jello recipe for the weekend
Ballistic Gelatin Recipe
The target material is prepared from gelatin, USP. The government laboratories purchase this as Pharmagel A, Type 250 from the Kind & Knox Co., Park 80 West, Plaza 2, Saddle Brook, NJ 07662. The last time I bought any was in 1984, and at that time the price was $2.40/lb., or about $600 for a 55 gal. drum, shipped F.O.B. from Sioux City, IA.
The powder is mixed 10 percent by weight in warm, but not boiling water until dissolved, and then poured into moulds and chilled in a large refrigerator. The standard block size is 15x15x30cm for handgun bullets and 20x20x50cm for rifle bullets, but improvised moulds such as from cal. .50 M2A1 ammunition cans work well.
You will also need Thymol or cinnamon oil as a clarifier, which is added in the proportion of 1 drop per liter. You will also need heavy duty electric stirrers or an industrial mixer, moulds, a release agent, such as Pam cooking spray for releasing the castings, LD plastic film or Saran wrap for wrapping the blocks, a freezer for storage if you will not use the blocks within a week, and foam coolers to transport them to the range, if you do not have a walk-in cooler near your lab.
To do this right, establish the tare weight of a 5 gallon stainless steel container in which you will heat the water and mix the gelatin. Ideally this should have a spigot on the bottom to aid decanting the dissolved gelatin into the moulds. Add 12 liters of water to the container and bring the temperature to 65 degs. C and adjust the weight by adding or deleting water to obtain 12,000 grams. Place two electric stirrers into the hot water, one near the top and the other near the bottom of the container. Add three grams of Thymol or 12 drops of cinnamon oil and stir until dissolved in the hot water. Add 1500 grams of Pharmagel A to the hot water, breaking up any lumps with a stainless steel rod or paddle, to supplement the stirrers, as necessary.
After the gelatin is dissolved, in 10-15 minutes, turn off the stirrers and remove them from the solution. Allow the bubbles and foam to rise to the surface for 20 minutes. If the container used does not have a spigot at the bottom, it is necessary to skim the foam off the surface before transferring the solution to the moulds. Allow the warm gelatin to stand at room temperature for at least one hour after transferring, so additional foam which rises to the top may be removed.
Place the gelatin in a refrigerator overnight at 0-5 degs. C. The gelatin may then be removed from the moulds by placing the container in hot water. After 15-20 seconds use a spatula to loosen the gelatin from the sides of the container. After two minutes remove the mould from the hot water and invert it over a piece of plastic film spread on a flat surface.
Once the gelatin is removed from the mould it should be allowed to remain at room temperature for one hour, then tightly sealed in plastic film and the wrapped block inserted into a plastic bag, which is again sealed to prevent evaporation, which drastically changes the consistency of the gelatin. Once tightly wrapped, the blocks can be stored up to six months in a freezer, or up to one week in a refrigerator. Unused blocks should be frozen immediately to retard mold growth. Before firing the blocks must be allowed to thaw and stabilized overnight at a temperature of 5-10 degs. C, because proper consistency is a function of the tempoerature.
Evaluation of the blocks is best accomplished by flash X-ray photography which permits measurement of transient cavity volume as a function of projectile striking velocity, time, distance penetrated and projectile exit velocity energy deposit). If high speed photographic equipment is not available, it is useful to use a small caliber calibration test shot, such as a steel .177 air rifle shot from a Daisy pump-up air rifle known to give consistent performance, which can be placed as a consistency calibration check in a corner of the block out of the way. The permanent cavity can then be made to stand out well for still photography by injecting a colored water solution of ten drops food dye to a liter of water, using as veterinary syringe or laboratory wash bottle to reach all corners of the permanent cavity. To provide proper scale for the photograph, a piece of graph paper can be photocopied onto overhead transparency film, and used as a template to be positioned over the shot. The block should then be placed on a light table or photographed using diffused, backlit strobe flash. Detailed ammunition test methodology is available in various open-source medical and technical references.