There are a lot of different tanning systems available. You will also hear all sorts of strange systems - some will work ok, but none will work as well as a good modern system.
Beginners - In my book, I used methylated spirit straight out of the bottle. You can get the purple stuff in any hardware shop. Industrial meths is the same, but has no dye in it. The reason I didn't use a more complex tan solution is that I wanted your attention focused on producing the squirrel. Meths is fine for small mammals especially when you're a beginner.
Intermediate - Paint on tan solutions are a halfway house to a full tan and are easy ie. just paint onto the skin.
True tanning of a skin can get complex.
Below are some useful links and information on tanning:
Tanning Chemicals Reference Chart
This info is from Van Dyke's Taxidermy Supply
|Tanning Chemical||Type of Tan||Other Materials||Amount Needed to Tan
2 Deer capes or 4 Fox skins
|Color of Hide After Tanning||Leaching of Chemicals
|McKenzie Tan||Brush On Tan||Salt, McKenzie Ultimate Acid,
Baking Soda, McKenzie Relaxer/Degreaser
|8 Ounces||White||No||Hair On Tan||Soft, Stretchy Leather|
|Krowtann 2000||Soak||Sodium Bicarbonate||8 Ounces||White||Yes||In House Tanning||Sets Hair, Pliable Leather|
|Ammonium Alum||Alum Tan||Tanning Oil, Salt, Pickling Crystals||1 1/2 Pounds||White||Yes||Hair On or Hair Off Tanning, (can add brighteners and silver toners to alum).||Sets hair, but skin will shrink. Firm but pliable leather.|
|Potassium Alum||Alum Tan||Tanning Oil, Salt||Paste Tan
Can be re-used
|White||Yes||Hair On or Hair Off Tan||Sets hair, but skin will shrink. Firm but pliable leather|
|Aluminum Sulfate||Alum Tan||Tanning Oil, Salt, Pickling Crystals||2 Pounds||White||Yes||Hair On or Hair Off Tan||Sets hair, but will shrink. Firm but pliable leather|
|Vegetable Tan||Tanning Oil, Salt, Pickling Crystals||2 Pounds||Pale Brown||Very Slow||Hair Off Tanning, Cow hides, Dyeing Tanned Hides||Dense, Firm or Solid Leather|
|Curatan®||Oil and Mineral Tan||Salt, Pickling Crystals||8 to 10 Ounces||Light Buckskin||Slow||Hair On or Hair Off Tan||Soft, Stretchy Leather|
|Tannium®||Chrome Tan||Tanning Oil, Salt||1 Pound||Pale Blue or Green||No||Hair On or Hair Off Tan, Garment Tan||Soft Leather|
|LUTAN FN||Alum Tan||Tanning Oil, Salt, Pickling Crystals||1 Pound||White||Very Slowly||Hair On or Hair Off Tan, Garment Tan||Soft, Stretchy Leather|
|Liqua Tan||Syn Tan, Synthetic Tan||Salt, Pickling Crystals||2 Cups||Cream||No||Hair On or Hair Off Tan||Sets Hair, Firm Leather|
Tanning with HQ Tan 5000
See links below for more advanced tanning info:
McKenzie tanning videos below:
Paring the Skin
Tanning the Skin
Hope this helps.