How to choose clay: bar vs mitt, and what grade
The first fork is bar or mitt. A traditional clay bar is a soft block you knead and glide across a lubricated panel; it’s gentle and cheap, but it’s single-life insurance — drop it and it’s trash. A clay mitt (or clay towel) has a rubber-polymer face bonded to a wash mitt, so it’s reusable and much faster over big panels, and if you drop it you just rinse it clean. The trade-off is that mitts tend to marr the surface a little more than a soft bar, so plan to follow up with a light polish afterward.
Grade: fine for maintenance, medium for neglected paint
Grade is how aggressive the clay is. A finegrade is the safe default for a car you keep on top of — it lifts light contamination with the least chance of marring. Step up to a mediumgrade only when the paint is genuinely neglected: years of unclaimed fallout, overspray, or a rough “sandpaper” feel that a fine clay can’t clear. More aggressive clay works faster but leaves more fine marring behind, which is another reason heavier decontamination usually pairs with a polishing step.
Always use lots of lubricant
Whatever you choose, the clay has to float on a wet film. Soak the panel with a dedicated clay lubricant (a good soapy wash solution works in a pinch) and keep it slick the whole time — if the clay ever grabs or squeaks, add more lube. Running clay on a dry-ish panel is the fastest way to put fresh scratches into the finish. For the full technique, see how to use a clay bar, and if you’re not sure clay is even the step you need, start with what paint decontamination is.
When to clay
Clay is a periodic job, not a wash-day habit — for most cars, once or twice a yearis plenty, or whenever the paint fails the “plastic-bag test” and feels rough. The single most important time to clay is right before you protect: because a wax or a ceramic coatingbonds to whatever is on the surface, claying first means the protection grips clean paint instead of sealing grit underneath it. If you’re going all the way to a corrected finish, clay first, then polish with a dual-action polisher, then coat — in that order.