I just tried an experiment using treated (and plain) denim.
I mentioned it to a local Tripoli member. He replied:
"I used a cotton bag for the Vulcanite for years
It eventually got impregnated with enough stuff to char to nothing on the ground
Fortunately it didn't cause a fire or damage the rocket but the was nothing left of it but ash on the ground"
My experimental method:
I used a pair of worn denim jeans that were in good shape. I cut off one leg and removed all the stitching. I then machine washed the fabric (no softener). I cut three 6" square pieces. One piece was left plain (untreated), the other two were soaked in likely fireproofing substances. The untreated denim measure 0.035" in thickness, and weighed 10.9 g.
The two chemicals tested were sodium bicarbonate and washing borax.
A cup of tap water was added to a two quart pot and set on an electric element set on "HIGH" When the water began to boil, an excess of the chemical under test was added to the boiling water to form a supersaturated solution. After allowing the solution to regain boiling, the liquid portion in the pot was decanted onto the fabric sample in a rimmed plastic plate. The solution was allowed to soak into the fabric for 5 minutes, then removed and hung over the sink to drain. Each sample was hung in the garage overnight to dry. After drying, the borax sample weighed 28.8g, the bicarb sample weighed 23.6 grams.
Note; both samples became stiff from the dried chemicals, the borax extremely so. No attempt was made to bend or fold the fabric to make it more supple, other than described below.
Three 2" squares of common typing paper were prepared. One gram of FFF Goex powder was measured onto each square (it's what I had on hand). An unmodified Estes igniter was placed in the center of the powder charge, the paper was folded around it, and secured with masking tape. The individual fabric samples were folded into quarters, the powder packet inserted. The fabric samples were held closed with a plastic spring clamp along one edge.
The samples were taken outside to the driveway, and the powder samples ignited electrically by remote.
Restlts: black soot marks were observed on every sample. No samples showed more than cosmetic damage. No charring, no smoldering, no fire was observed on the samples immediatle after igniting the powder packets.
Conclusion: untreated denim may be suitable for limited use as recovery protection. Its condition would need to be inspected prior to each flight. The useful life may be extended by the use of common houshold chemicals as fireproofing agents.
Pictures:
powder packet with 1 gram of FFF powder
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Estes igniter placed in packet
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taped packet
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test proceedure
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results: sodium bicarbonate; washing borax; plain
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