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Hello! I have a quart of 10% solution of permethrin which I would like to dilute to 0.5% for application on clothing and gear for an upcoming trip. I can add a quart of water and get 5%, then add 2 quarts of water and get 2.5%, etc. But, I’d like to use a mixing formula so that I can end up with just enough solution to treat my clothes, and have that be repeatable. Any chemists out there? Thanks!!
Mix 1oz permethrin with 19oz water to make 20oz of 0.5% permethrin, if I did the math right. If I did it wrong, it likely won’t matter if you have 0.5% or 0.476% or 0.526% or something like that. I think most medicine cups are 30ml or about 1oz. A measuring Tablespoon is 0.5oz. Don’t use it for medicine (or food or anything you consume) after you measure permethrin with it! Some spray bottles have ounce markings on the side that aren’t accurate enough to measure the permethrin, but you could measure the water that way and it would be close enough.
I don’t know how much you need total. It depends on the number of outfits and if you’re spraying or soaking it.
My math came to the same conclusion…19 parts water to 1 part 10% solution results in a 0.5% solution.
This is not an answer to your question however it may be easier for you. If you mix your 10% permetherin 1:12 with water then soak clothing in a bucket over night, hang dry and wash, your clothing will remain treated for up to 50 washes.
All good info and I appreciate the help. I sprayed and it turned out that I had enough Sawyers to do the job. We are hiking in CO starting next week, and I’m under the impression from my earlier hikes that spraying is adequate. I’ll be treating again in Sept to hike in Maine. I may try the soaking method for that. Thanks again for the great info!
Where are you hiking? I just got back from near Steamboat, and there were the worst mosquitoes I’ve ever experienced.The snow just finished melting out in the past few weeks where we were camping. I only had Picaridin insect repellent, and it mostly worked but they were still obnoxious and swarming around us. I would have liked to see what effect Permethrin had on them. It also would have been interesting to compare DEET and Picaridin because, although both are effective at preventing bites, I suspect DEET is better at keeping them a little farther away.
Normally the bugs in Colorado are not bad at all, so this seemed unusual. Let us know how it was for you!
Interesting thread. I have a small bottle of black fly repellant that WORKS! I dunno what it is but it does not smell like DEET (which seems not to work against black flies anyway).
Got it in Michigan near the AuSable River years go and it still works Even sand flies stay away from it. So gar the bottle has not dissolved so that, at the least, may mean it’s not a solvent. ;o)
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