Monday, August 29, 2016

Oil and Glue: Arch Enemies

Did you know that you can remove those pesky little splotches of glue on your leatherwork by dabbing them with oil and wiping them away?  Somewhere along the way I picked up this handy little tidbit for leather working, and it’s worked well any time I’ve had to use it. 

But what happens when too much oil comes in contact with important areas of glue? 

Nothing good, that’s for sure.

I once had a friend bring me a lovely dressage bridle for repair. Some of the stitches were loose on the mass-produced (however high-end) reins and noseband, and she basically wanted me to tidy the whole thing up a bit. When she presented me with the bridle I immediately noticed a shiny goo coating much of the noseband. When I asked her about it, she said that it had been consistently leaking glue ever since she’d gotten it. 

I admit at first I was stumped. I had thought maybe they’d used the wrong type of contact glue when constructing the bridle, or perhaps the heat from being in the car had melted it. Perhaps some overzealous chap had slathered on just a little too much glue, or maybe the padding in the noseband was reacting poorly with the chemical makeup of the adhesive. 

Alas, after some more discussion, I learned that she had soaked the bridle in oil after receiving it from the manufacturer. This is a common practice in the horse world, and often it’s not an issue - apart from loosening and stretching the leather fibers and weakening the integrity of the bridle (but that’s a whole other can of worms!) 

In this case, however, the manufacturer had used lots of glue to make sure their bridle was well constructed and strong. The noseband was a complex design of many layers of leather and foam, all of which had to adhered to one another just-so, in order to stitch up correctly. I'm not opposed to this, especially when laying down several layers, but unfortunately when this newer practice of using lots of glue meets with the older practice of soaking new tack in oil a serious problem arises. 

You see, oil likes to break down polymers and act as a solvent, and many of the glues used in leather working are solvent-based, which means they are polymers suspended in a quickly-evaporating solvent. This is why they give off such a terrible smell when wet; the nasty solvent is actually evaporating into the air you're breathing. Delicious! 

Because oil acts as a solvent to many polymers, when it comes in contact with these "fast drying" adhesives it begins to re-distribute the now-dry adhesive throughout the oil. Worse than this, the oil actually begins to break down the polymer chains, creating less and less stable adhesive until finally it gives way to goo. Fascinating, and unfortunately a recipe for a sticky mess! 

So hopefully you've stumbled across this point before it's too late, though I suspect a high percentage of readers will find this as a result of searching the internet for "Help! Bridle leaking glue!" 

What do I do when I first bring home a new bridle or piece of leather? If it is stiff and dry, I oil it in light coats with a sponge, layer by layer, until the oil begins to absorb more slowly. That's the leather's way of saying "No thanks! I'm full!" Then I leave it to sit for a few days and finish it off with a layer or two of protective leather balm - something beeswax-based and not glycerin-based (I make and sell my own small-batch leather balm - shameless self plug!) 

To be honest, if I bring home a piece of tack that is soft and supple, I tend to just slap a coat of leather balm on it and leave it at that. Oil is good for leather that is starved of moisture, such as old stuff in danger of developing cracking, but apart from that it actually softens and weakens the leather so I don't use it much!