Source: LilCliffy The Cobbler & Researcher
Oil-based treatments do wonders for conditioning and maintaining leather. But there are two results of using the oil that may cause problems:
- 1) It greatly softens the leather- so much so that the boot may become so soft it loses its supportiveness.
2) The oil will impregnate the liner of the boot as well. This is a good thing if the boot has a leather liner- but, if the liner is meant to act as breathable and/or waterproof layer, the oil will impregnate the pores of the liner and cause it to no longer be breathable (= sweaty, wet, cold feet), nor waterproof. Once the liner is impregnated with oil- it is for life.
Wax-based treatments do not condition and maintain leather- they simply create a waterproof coating. It does work. However, apparently wax reacts with adhesives used to glue and resole boots. So- if you think you would like to resole your boots- DON'T use a wax-based product to waterproof the leather. Some boot cobblers won't even try to resole a boot if they find out it has been treated with wax.
I use water-based leather treatments to condition, maintain and waterproof my leather boots. You can absolutely saturate the leather with the stuff- without over-softening the leather and without ruining the liner. And with the leather regularly conditioned, it almost lasts forever- unless it gets cut.
Anyway- I may seem a bit nerdy and obsessive about this- it is based on 25 years experience- and experiment/research- wearing quality leather boots in the field in all seasons and all climates, as a professional faller, forester/field technician, and backcountry skier. I have spoken to many cobblers and leather boot manufacturers about this as well.
High-quality leather boots with synthetic liners that insulate, breathe and even repell water are the BOMB man. And the way to maintain them is with a water-based treatment.
I worked as faller on the West Coast in the mid-1990s- temperate rainforest. I bought a pair of high-quality, old-school, full grain leather faller's boots, with welted soles. Based on the tradition- I treated them with mink oil- constantly- it turned them into slippers, and my feet were wet for two years straight...
The Zamberlan HydroBloc cream is the exact stuff that I use religiously on all of my leather boots. I cannot say enough good stuff about it. It is water-based, designed to both condition and maintain leather- as well as keep it waterproof. There are a number of other manufacturers of similar products including Scarpa, Nikwax, etc. The only reason I prefer the Zamberlan product is because I have been able to get it easily (MEC), and at a good price.
To get maximum absorption you actually need to get the leather soaking wet. I do a thorough saturation about 2-3 times a season (the last one being before I store them). I wrap my boots in soaking wet towels and leave them in a utility sink/bath for a few hours. The absorption of the cream is amazing- when the leather is wet. Other than that- I spot treat the flex points of my boots every time I take them off- just to prevent eventual weakening and cracking of the leather. The full-saturation of the leather will make them completely waterproof and protect the leather from drying, cracking, and abrasion (even the typical abrasion caused by crust and vegetation).
The fact that it is water-based is important and confusing. The water-based products have at least two key attributes. One (as others have pointed out): it doesn't over-condition the leather and undermine its strength (i.e. the boot will maintain its stability). Two: it doesn't alter the characteristics of the boot's inner liner. On the second attribute- if your leather boots have an inner, non-leather liner (i.e. designed to improve comfort; wick moisture; insulate; water-proof; etc., etc.)- a water-based treatment will not damage the liner. For example- the Alpina Alaska has multiple inner liners and foam designed to: insulate; provide support and stability; a custom fit; moisture-wicking; and waterproof. Of course other manufactures have similar designs. An oil-based product will saturate these inner layers and they will fail to insulate properly; they will no longer be waterproof; and they won't breathe. In other words- your feet will be wet and cold.
At first it seems counter-intuitive to apply leather waterproofing treatment to wet leather...for years I used to make sure the leather was as dry as possible- with mediocre results. Then I got instructions for applying to wet leather (from the manufacturer)- and the improvement in absorption was like night and day. Not only is the absorption more effective (i.e. it penetrates deeper)- I also found that I end up consuming less cream, and doing less applications per season.
Cream versus Spray
The spray products are designed to waterproof suede, split leathers, nubuck, etc.- with a focus on preserving the aesthetic or cosmetic qualities of the leather (i.e. look and feel). The spray products will "waterproof" the leather (only temporarily)- but they will not condition the leather, nor protect it. I have never gotten more than a few hours of waterproofness out of a spray product. However- a cream product will completely change the aesthetic of a split leather- it will darken and become smooth (and your Alaskas will become red). To be honest- I am somewhat convinced that the split leather of a boot like the Alaska is actually purposely designed to encourage absorption of cream treatments (many mountaineering boots have a split-leather outer as well). As alternate example- my current pair of heavy-duty backpacking boots are thick nubuck. Although the nubuck is beautiful and tough- I find it frustratingly difficult to treat (if the boot didn't have a GTX liner I kinda doubt I would be able to keep it waterproof). Unconditioned full-grain leather (i.e. not nubuck), and split leather is much more absorbent.
Oil-based products will over-condition the leather (as others have said) making it soft and weaker (this may be desirable in an extreme boot like a heavy-duty leather logger's boot). For a ski boot it would turn it into a floppy slipper.
Products like "sno-seal" are made from beeswax. Beeswax is an excellent waterproof treatment- but it will not maintain and condition leather. Another note- and this is important: if you plan on re-soling your boots don't use a beeswax product. According to the manufactures and the cobblers- beeswax will prevent proper adhesion of glues, when putting on a new sole. And apparently- once you have applied beeswax- it is impossible to get rid of the residue. So if you've got a boot with a traditional welted sole- I would not recommend a beeswax-based treatment.
With the leather wet- the water-based creams fully penentrate deep into the leather. Oil-based treatments are equally effective, but have all the negative side effects.