Today it’s increasingly common with sanding down leather, mainly to remove cracks, but sometimes also only to smoothen out creases or to remove dye before doing patina. However, when removing the top layer of the grain surface, the leather becomes more sensitive, which one need to be aware of. Here’s pictures and a film to prove the case, and a bunch of leather knowledge as a bonus.
It’s not a new thing to sand down leather. It’s been done for hundreds of years when repairing a damaged surface of full grain leathers with cracks and stuff, and it can then be restored to look neat and nice again. When doing this type of refurbishment, people have been fully aware that albeit one can restore the look, the properties of the leather is harmed, you will end up with a pair of shoes or leather product being inferior to what it once was. If you know this to be the case, you can make an informed decision on what will be best, a less sensitive but less good looking leather product, or a nicer looking but more sensitive one. No harm in this.
Entering internet era, and a bunch of “experts” spreading the word on how easy it is to sand down leather and make it all look good again, and sort of like with The Telephone Game, this starts to be derailed and on YouTube, forums, social media etc people start sanding even the smallest of cracks, or to remove healthy creases or even just get rid of dye before painting the shoes again. All this without mentioning the fact that one of the most important properties of full grain leather, its resistance and durability, will be harmed.
When a full grain leather is tanned and smoothed, it will result in a top part of the grain which is denser and more solid than the centre of the hide. It’s extra evident on this leather here, where the dye only have penetrated this part, and you can see it on the picture below. If you hava a full grain leather, you can feel how the centre is a bit more porous, with this top area that feels almost like a separate, denser part attached over the rest of the hide. It’s in this that you can see the pores. And it’s this outer grain surface that stands for a lot of the resistance, the reason why you don’t need to use waterproofing sprays or similar (and not should, since it prevents nourishing ingredients of shoe cream to penetrate next time you polish the shoes, which will harm the leather in the long run when it doesn’t get the nourishment needed, it will sort of “dry out from inside”) as on for example nubuck or suede that doesn’t have this. And it’s this protective part that you remove large parts of when you sand the leather.
To showcase the problem with sanding down full grain leather, I did my own “experiment”. I cut out four pieces of full grain leathers from two different hides from the French tannery Annonay. One of each was sanded down with very fine sandpaper, one just very lightly, while one more heavily, which is more similar to what is done when people do these “restorations” of leather. The lighter sanding is mainly the case for when cobblers do repairs on heavy scratches, and apply a special kind of repair paste. To have this to stick, they need to rug the surface of the leather.
After this all four leather pieces are treated the exact same way, with two layers of shoe cream (although should be mentioned that the sanded one absorbs much more cream, than the untouched ones) and two layers of wax polish. I used Boot Black for the dark brown pieces, Saphir Medaille d’Or for the light brown ones. I then splashed water on them and let it sit for 15 minutes, before wiping them off and leave them to dry.
As you can see clearly in the pic above and the film below, it’s quite evident that the heavily sanded piece of leather absorbs the water quicker than all the others. The lightly sanded one isn’t really any difference to the original one, there it’s so little of the outer grain that’s been touched, so it’s more or less intact. The most sanded piece also gets a quite big bumps from the water, like very big water stains, compared to the smaller bumps on the other pieces. Also, after they have been allowed to dry completely, you can see how three of the pieces are more or less back to their original state, here the grain have protected the leathers fine, while the heavily sanded piece have been darkened and got slightly discoloured stains. Now, this was only water, imagine what some more harmful substance can acquire when the protective outer surface of the grain have been removed.
If you are to sand down leather, for one reason or another, think it through if it’s worth it. And if you do, it might be worth it to cover it with a more protective product that can sort of replace what you have removed. There’s various stuff available, which sort of will create something similar to corrected grain (and that’s basically how corrected grain leathers in tanneries are done as well, the leather is sanded and then covered with a new outer surface). The important thing is to be able to do an informed decision.