THE NUANCES OF BUCKING HIDES

Bucking is the act of turning hides alkaline before scraping the hair and/or grain away. We can do this through soaking hide with water + an alkali or by directly rubbing an alkali onto hides.

Alkalinity is tough to define.  We have to think of the pH scale to conceptualize it. The pH scale is on a spectrum from 1 to 14.  This means 7 is “neutral," neither acidic nor alkaline.  1-6.9 is acidic. 7.1 to 14 is alkaline. Acidity preserves hides.  Alkalinity transforms them. The “pH” stands for “potential of hydrogen” which is beautiful rabbit hole a bit too much for this email, but look it up if you're curious to get a deeper grasp. 

There are two popular alkalis: lime (calcium hydroxide) and lye (potassium or sodium hydroxide). Use 2 cups lime per 6-10 gallons of water. For lye (which varies in strength) follow a recipe that will give you a reading of 9 on the pH scale.

(1) Length of bucking time

At 7-10 days of soaking, the hair will start to ‘slip’ from the follicle. You'll be able to tug the hair out, with a little bit of resistance. The hide is not ready to be wet-scraped for a drum or any grain-on product.  But it is ready to be wet-scraped + grained.

At this point in time, the grain (the outermost layer of skin, where the epidermis rests) swell and becomes vulnerable.  It takes on a pink or gray colour, as opposed to the dermis underneath which takes on a yellow colour.  The colouration is all due to the alkali - the hide will return to white after we neutralize it.

This is the perfect time to grain a hide: while the grain is porous and spongey.  Before the alkaline soak, the grain was thin and brittle.  After 10 days, it will settle down and become tacky, glueing itself to the dermis.

At 10-14 days of soaking, the grain firmly re-attaches to the dermis and loses its sponginess.  The hair starts to slip out easily, possibly just falling out and floating in the water.  This is the perfect time to wet-scrape a hide leaving the grain on. There is less chance that'll damage the grain once it has settled + once the hair is falling out freely.

(2) Temperatures

 This where lime and lye act differently.

Lye is thermo-sensitive. A bucking solution will get stronger (more alkaline) when heated.  It can so strong it dissolves a hide, especially if you've made homemade lye from wood ashes.

Lime is more stable. And it prefers cooler temps. Its peak alkalinity is around 10 degrees C.

However, the strength (alkalinity) of our bucking solution's pH isn't the only factor we need to consider.

Warmth also loosens the grain more, and thus expands the hair follicles, which lets the hair slip from the hide. This is key.  A cool lime solution can be highly alkaline but the hide might hold on tight to its hair follicles.  If you want to easily slip the hair, you want warmth. Room temperature is a safe bet for any bucking solution.

(3) The little details that matter (painting on lime)

For years, I just poured 2 cups of powdered lime into my tub of water and put the hide in. I didn't think about it too much.  

Then I started to notice how in every other step in hide tanning, if we put a little more front-end effort in, we get an easier time later in the process - and nicer hides.

I learned from Billy Metcalf that if we soak hides in water for 24 hours before bucking, the fully rehydrated hide will have its dermis + grain separate beautifully.  I learned from tanning books that flushing a hide with water after bucking will remove the extra ground substance (which was loosened/partially dissolved by bucking). And I learned from observation that if we paint lime on a hide first, before soaking in water, we get a much more thorough bucking.

I do all three of these techniques now for my bucked hides, and the hides are easier to scrape and soften.