Full grain is the outermost layer of the hide with the grain surface left intact. Nothing is sanded, buffed or embossed. That single fact is why it is stronger, why it costs more, and why it is the only leather that looks better after five years than it did new.

Why it is stronger

A hide is not uniform. The fibres near the surface are dense and tightly interlocked, and they get looser and more open the deeper you go. Full grain keeps that dense top layer, which is why a full grain strap can be 3mm thick and take your body weight, while a genuine leather strap at the same thickness stretches and then tears. It is also why we can saddle stitch rather than glue: the leather is strong enough to hold a stitch under load.

What the marks are

Every full grain bag has marks in it, and they are not defects. Healed barbed wire scars, insect bites, stretch marks around the belly, a slight colour shift where the hide was thicker. A tannery sanding those off is exactly what turns full grain into top grain. We cut around the worst of it and we leave the rest, because removing it means removing the strength with it.

How it ages, month by month

For the first month it looks close to the photo. Between months two and six the handles darken first, because that is where the oils from your hands go in. By the end of the first year the body has deepened a shade or two and the corners have started to burnish. After two years a tan bag is chestnut and a chestnut bag is close to dark brown. This is the patina, and it is the entire point.

How to tell full grain from top grain in a shop

Look at the surface at an angle under a light. Full grain has an irregular pore pattern that changes across the panel, because skin is irregular. Embossed top grain has a pattern that repeats, because it came off a plate. Then look at the cut edge: full grain is the same colour through the thickness or slightly paler, while a coated split has a distinct skin over a fibrous core. Finally, press a thumbnail in gently. Full grain marks and the mark fades. A finished split does nothing at all, which people mistake for quality.

Looking after it

Very little. Keep it out of direct sun, wipe it dry rather than wet, and put a neutral conditioner on two or three times a year. Full instructions are in how to care for a leather bag.