Most people who own a leather bicycle saddle know they’re supposed to treat the leather with a conditioner and waterproofer to soften and preserve the leather. Brooks makes a big point of this and markets “Proofide”, their proprietary paste of a blend of various waxes and oils. They also make a point of not over-applying their product: saturating the leather can soften it too much and make the saddle too saggy. Perhaps that’s one of the reasons they sell it as a paste and not a liquid. In fact, on the burnished side of the leather (the side you sit on), the paste doesn’t even penetrate (burnishing seals the surface of the leather and gives it that smooth feel). You apply it like a polish, then buff it out. Since the paste doesn’t penetrate the burnished side of the leather, it doesn’t usually affect the color (soaking oil into leather darkens it considerably).
I recently bought a Minnehaha saddlebag for my Shogun touring bike. Like many saddlebags, it has leather straps, but they are natural colored, very light:
I also purchased a new Brooks saddle in “honey” color for the same bike (not the saddle in the above photos), and wanted to darken the leather on the Minnehaha saddlebag to match. I tried using neatsfoot oil, since that’s generally regarded as the oil of choice for conditioning leather. However, after testing neatsfoot oil on a small section of leather and finding that it does indeed soak in and darken the leather, I later discovered that the color darkening was only temporary. Within a couple of days the leather lightened up again! It was as if the neatsfoot oil evaporated (a plausible idea, because I don’t know how much of a solvent base there is in the neatsfoot oil I bought). So, I wanted to try a more permanent treatment. I rubbed in some Proofide paste, and found that it darkened the leather a little bit, but not as much as I wanted. I wanted a dark honey color. I wondered if “forcing” more Proofide into the leather would make the leather darker. So, I decided to pre-heat the leather, so the Proofide would melt upon application. My hypothesis is that the melted Proofide would soak into the leather, then as it cooled down again, it would again become a non-volatile solid (it wouldn’t evaporate). To do this, I simply placed the saddlebag in the oven at 200 degrees for a few minutes. Then, I used an old toothbrush to apply the Proofide to the hot leather.
Proofide has roughly the same consistency as soft butter, and it melts upon contact with the hot leather much as butter does on a hot skillet. Wow! The leather soaked up the melted Proofide like a sponge! Compare the two treated straps on the left with the untreated strap on the right:
I found that the leather cooled down very quickly, and I had to keep returning the saddlebag to the oven every 5-10 minutes to reheat. Also, after a while I ditched the toothbrush in favor of just using my finger to spread the Proofide (I wore nitrile gloves the whole time). Here’s the finished bag:
And in case you’re wondering whether so much Proofide on leather is potentially damaging, well, I am inclined to think not, at least in this case. In the case of a saddle, which has to support a lot of weight, I would agree that too much Proofide may overly soften the saddle, compromising its ability to properly support the weight of the rider. But since saddlebag straps don’t have much of a structural role, I doubt excess oil/wax can cause any harm. At any rate, the straps that attach the bag to the saddle are replaceable should they become weakened.
Another idea for the adventurous is to experiment with wood stain. Wood stain of various colors can be mixed with Proofide (maybe melt the Proofide to mix with stain, then let harden again). This might result in even darker tones to match darker saddles.