Advice and questions on keeping your instruments in top form
People have reported that Shea Butter and Beeswax aren't satisfactory solutions, so I gave it some thought, and here's what I've come up with. Let us know if you try any of them, or have other ideas!

Of course any treatment will affect the sound of the skin, but personally I think it's worth some trade off to have an "outdoor" drum for humid weather. Hopefully we can find something that sounds better than synthetics, but performs better than untreated skin!

Nothing will prevent humidity forever, as water molecules will permeate any barrier eventually, but they can slow it down, and/or provide reinforcement and stiffness to prevent the fibers from elongating and losing tension.

-Tung Oil - a special oil that dries and forms a polymer (plastic) by cross-linking with itself. Takes a couple weeks to cure. Can be bought online. Dries to a non-tacky coating. Tips from woodworkers include: Dilute with solvent for better absorption on the first coat. For this I use essential oil in the form of "Citra-Solv: Citrus Magic" which is a cheap household cleaner made of citrus peels. 100% natural.

-NikWax makes a spray for leather gloves that makes them waterproof, and it's relatively non-toxic, made from zirconioum acetate dissolved in propylene glycol. May require re-application, as it doesn't form a durable surface.

-Boiled linseed oil - Basically this is the skin version of oil-cloth or "oil skin", which came from sail cloth, then sailors wore raincoats made of it. Same concept as Tung oil, but it's sometimes easier to find. Yellows more over time.

-Spirit varnish (tree rosin dissolved in essential oil) - it's a bit stiff if applied generously, but can be mixed with small amounts of oil or wax to soften it, and a very thin/dilute coating is all that's needed to resist water. Will brighten the sound, so best on skin that's the opposite (cow, or soft goat). Rosin is not the same as resin/liquid sap. Rosin is resin that has been heated to dry and harden it, or has naturally dried and hardened. Resin takes too long to dry. Also, gum is not the same as rosin. Gum is alcohol/water soluble. Same with true Shellac.

-Carnauba wax - also diluted very thin. I don't recommend shea butter or beeswax, because they tend to dampen the sound, and aren't actually waterproof, but Carnauba is a lot harder and less "mushy", so it might sound ok. Used in formulas for car wax and surf board wax.

-Rennaissance Wax or Microcrystalline Wax - even harder and more durable than carnauba. It's petroleum based, so not as eco-friendly, but relatively non-toxic.

-Latex - very very dilute (30:1 water to latex), soak skin in it before heading the djembe. If dilute enough, it should merely coat the fibers. Might dampen the sound, so might be better if the wet-pull isn't very tight. This way the latex can be stretched out a bit with the final pull. Highly experimental, but also highly waterproof.

-Other waterproofing treatments, such as Polyurethane, or hydro-carbon based sealants. Always check the MSDS on any product you consider, as some contain toxic solvents, such as MEK (methyl ethyl ketone).[ A quick search for "product name msds" usually works.] Polyurethane stretches too, not as much as latex, but it won't dry hard.

-Combinations of above treatments might be even better, such as dilute tung oil, allowed to cure, followed by spirit varnish. The idea being to combine features (tung dries soft and flexible, varnish is hard and stiff, so both might be better than either alone).

***But I strongly WARN AGAINST anything containing PFCs, this includes Teflon, Armour-All, Scotch-Guard, and MOST outdoor gear waterproofing treatments. PFCs are flourocarbon based compounds, and they are much worse than hydrocarbon based waterproofing, for your body and the environment.***