The impression is the single thing that determines whether your piece fits. It is also genuinely easy to get wrong on the first attempt, which is why every kit we send contains enough putty to do it twice.

Read it through first, then mix

The putty starts setting the moment the two parts are combined, so read the whole instruction card before opening anything. Have the tray in front of you and a mirror available.

Mix quickly and completely until the colour is uniform with no streaks. Streaks mean unmixed catalyst, and unmixed catalyst means a soft patch that distorts.

Seat it fully, and evenly

Press the loaded tray straight up (or down) onto the teeth in one movement, far enough that the teeth sink well into the putty. Rocking it as you seat it is the most common cause of a distorted mould.

Then hold still. Not almost still — still, for the full time on the card. Movement in the first minute is what produces a mould that looks fine and fits badly.

Check it before you post it

A good impression shows crisp, distinct tooth shapes with clear edges and no smeared or torn areas. If any tooth looks vague, do it again with the spare putty. That is what it is there for.

If you are unsure, photograph it and send us the picture before posting. We would far rather look at a photo than cast from a mould nobody is confident in.

We will reject a bad one

If what arrives is unclear, we tell you and post another kit free rather than casting from it. A guessed fit is worse than a week’s delay, and it is not recoverable once the metal is cast.

Once we have a good one, it stays on file. Your next piece needs no new impression at all.