Home-Made Ballistic Gel Additives – Chapter 2

Home-Made Ballistic Gel Additives – Chapter 2

In my last article, we reviewed a simple experiment I performed to evaluate the usefulness of hydrogen peroxide and bleach as additives for clarifying and preserving ballistic gel.  While crude, this initial batch of testing quickly showed hydrogen peroxide works.  In this article I’ll be discussing a much larger series of tests I performed to determine the best concentration for clarity, as well as other ways to extend the shelf-life of this gel.

Method

I began by mixing up a series of samples, each of which consisted of roughly a liter of gel poured into a Tupperware container.  All samples were  prepared using the same apparatus, with only the additives and concentrations changing from one to the next.  One sample was left untreated for use as a control, all others had 50ml of hydrogen peroxide added, in concentrations of 5, 10, 15, 20 or 29% (two samples each).  Half the hydrogen peroxide samples also received 2% volumetrically of proprionic acid.  Additional samples Samples were also prepared using both tapwater and distilled water to determine if there is any advantage of distilled over tap.

After 48 hours of refrigeration, each sample was compared to the control for clarity, color and consistency.  After three weeks each sample was re-checked for signs of mould.

Testing

Samples prepared included:

  • Distilled Water
  • Tap-Water (Control)
  • 5% Hydrogen Peroxide
  • 10% Hydrogen Peroxide
  • 15% Hydrogen Peroxide
  • 20% Hydrogen Peroxide
  • 29% Hydrogen Peroxide
  • 5% Hydrogen Peroxide / Proprionic Acid
  • 10% Hydrogen Peroxide / Proprionic Acid
  • 15% Hydrogen Peroxide / Proprionic Acid
  • 20% Hydrogen Peroxide / Proprionic Acid
  • 29% Hydrogen Peroxide / Proprionic Acid

Results – Clarity, Color & Consistency

The first thing I’d like to address is distilled water vs tap-water.  A number of folks contacted me after the last article asking me to compare the two.  I thought this was a neat idea, so here are the results.  The camera and lighting positions make it a little hard to tell, but if you refer to the video posted above you’ll see that other than a bit of particulate matter they turned out virtually identical.

Moving on to the 5% hydrogen peroxide, this is definitely the biggest difference in color and clarity.  As with the previous experiment, I don’t have any way to accurately quantify differences in color, but I’d estimate it’s roughly 50% lighter than the control sample.

This trend continues with each successive increase in hydrogen peroxide concentration, although the difference becomes less pronounced as they progress.  More critically, the gelatin becomes less and less rigid as the hydrogen peroxide concentration rises.  Compare the 5% sample shown in the video to the 29%, and you have to imagine this is going to have an effect on ballistic test results.

So how much hydrogen peroxide is too much?  I decided to find that out.  In the video you’ll see a block demonstrated that was made by replacing several liters of water with 29% concentrated hydrogen peroxide.  As you’ll see, it’s extremely clear, however it’s also riddled with bubbles formed due to the chemical reaction that takes place at that concentration.  Moreover, the density of the gel block has been affected dramatically, rendering it useless for ammunition testing.

Results – Preservation

The second goal of these experiments was to find a way to preserve our gel blocks so they can be stored without requiring refrigeration.  For this experiment, I wanted to test hydrogen peroxide as well as proprionic acid.  Proprionic acid is the chemical used by the food industry to preserve gelatin, typically at about 0.5-1% volumetrically.  I’m not planning to eat this stuff, so I bumped mine up to a full 2%.  Once the samples were mixed, I sealed them in Tupperware and left them at room temperature for three weeks.  The results, I think, speak for themselves.

The control sample shown in the video has obviously gone very, very rancid; suffice it to say I won’t be holding onto that one.  Aside from some wrinkling on the surface caused by evaporation and a bit of foam left over from when I poured it, the proprionic acid sample looks fine.  Likewise the 5% hydrogen peroxide blend remained similarly unspoiled.

For those of you wondering why I didn’t mention proprionic acid during the color testing, the reason is that it had absolutely no effect.  I tested it with each sample (as you’ll see in the video), so that’s one less thing to worry about if you decide to use it.

Density

Finally we’ve got density to think about. As we’ve already seen, the clearest gel block is worthless to us if isn’t dense enough to do the job, and consistent enough to be comparable to other people’s testing media.  After testing each sample using the FBI’s steel BB method, I’ve confirmed that the higher the hydrogen peroxide content, the weaker the gel’s bond.

Interesting Notes

I also came across two other interesting things during testing.  The first is that hydrogen peroxide in the gelatin will react with ferrous metals.  After shooting each block with a steel BB, I noticed after a couple days I could see small air gaps forming around them.  This is almost certainly caused by the chemical additives attacking the metal BB, causing it to form gas bubbles.  Fortunately I plan to measure my wound channels within a day or two of performing my test shots, so that shouldn’t be an issue for me.

The second interesting thing to note relates to the proprionic acid.  After a day or so, ferrous metals left suspended in the gel begin to rust as the acid attacks them.  In the case of my tests, once again, this was the steel BB.  Again, not really an issue since I wouldn’t ordinarily leave them inside.

Conclusion(s)

There is no practical difference between gelatin produced using distilled water and tap-water.

Hydrogen Peroxide and Proprionic Acid can be used to clarify, lighten and preserve home made ballistic gelatin and still FBI-grade specifications for testing purposes.  While proprionic acid does not affect density or consistency, hydrogen peroxide does.  To compensate for this, I’ve increased the amount of gel in my mixture to a 9:3 ratio of water to gelatin.  Added to this is an additional 5% volume of hydrogen peroxide diluted to 5%, and an extra 2% volume of proprionic acid.

This formula produces a mould-resistant ballistic gelatin that can be stored at room temperature.  When tested using my modified version of the FBI’s steel BB method, the resulting wound channel measured 2.625″, or 0.00583″ per foot per second.  That’s just .00003″ more than the previous recipe, and well within acceptable tolerances.

Final recipe
9:3 +5% Hydrogen Peroxide +2% Proprionic Acid

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