A gentle guide to conditioning, because the most common mistake is doing too much of it. Little and often, as always, and sometimes not at all. Additions welcome.
When conditioning helps
When it doesn’t
- Coated leathers and coated canvas: the product sits on top and goes tacky.
- Untreated vachetta: it darkens, sometimes unevenly.
- Suede and nubuck: conditioner flattens the nap and leaves dark patches.
Related threads: the thread on Sticky or stiff zippers on bags.
The routine, as short as possible:
- Clean first: a dry, soft cloth to remove dust.
- Test on a hidden spot (under a flap, inside a pocket edge). Wait until fully dry before judging.
- Apply a very small amount with a soft cloth, in thin layers.
- Let it absorb completely. Buff off any excess.
- Never on hardware, edge paint or stitching.
How often: when the leather feels dry, not on a schedule.
Blunt version for vachetta: don’t, unless you want it darker. Conditioner speeds up and darkens the patina, often unevenly. The patina thread has the details. 
Verdict on “conditioner fixes dry leather” on reps: it depends on what the leather is. Some rep leathers feel dry because they have a heavy surface coating, not because they lack oil. Conditioner can’t get through that coating, so it just sits on top and looks greasy. The “dry vs plastic leather” thread explains how to tell them apart.
Exactly right, and worth saying clearly: if conditioner beads up or stays on the surface, stop. That leather is coated. It doesn’t need it and won’t take it.
One more thing people get wrong: edge paint. Conditioner on painted edges can soften the paint and make it peel. Keep the cloth away from the edges.
Disagreement on one popular tip: rubbing hand cream or kitchen oils into leather. They’re often suggested. They can go rancid or darken the leather. A product made for leather, tested first, is the boring, safe choice.
The guide, with everyone’s additions:
Condition only if
- The leather is smooth and uncoated, and feels dry or looks dull.
Never condition
- Coated leather or coated canvas (product sits on top, goes tacky).
- Untreated vachetta, unless you want it darker.
- Suede or nubuck.
- Edge paint, stitching or hardware.
How
- Dust off with a dry, soft cloth.
- Test on a hidden spot; judge only when fully dry.
- A very small amount, thin layers, soft cloth.
- Let it absorb; buff off the excess.
- If it beads up or stays on the surface, stop: the leather is coated.
How often: when it feels dry, not on a schedule.
Avoid: hand cream, kitchen oils, anything not made for leather.
A photo of the hidden-spot test (inside the flap, soft cloth, a small amount of product) would help anyone trying this for the first time.
Good guide. The best conditioning routine is often none at all.
