It seems my faithful Nikon EM has sprung a light leak. Thankfully, my fellow Nikonians came to the rescue and last night I was able to (hopefully) repair the problem. Read on for the gory details.

1. Buy a light seal foam kit from Jon Goodwin (interslice) on eBay. Shipping time (to the UK) was about a week(!). The large $9 kit contains enough foam to do about a dozen cameras.
   When you receive the kit, unpack it carefully. Identify and label (using sticky labels on the backing paper) each type of foam strip based on the descriptions in the booklet.
2. Gather the tools recommended by Jon in his detailed instructions, most importantly the X-acto type knife. Cotton buds (“Q-Tips”) are also very useful for removing the crud.
3. Sit at a table with a clear workspace. Set up a good, close light, like a desk lamp.
4. Remove any mounted lens from the camera and fit a body cap while working on the rear. If the focusing screen is designed to be removeable, take it out.
5. Follow the instructions carefully. The most tedious part of the job is removing the old foam. Some kind of solvent (applied via a cotton bud) is useful to soften the adhesive; I used Surgical Spirit, which seemed to do the job well (NB. not sure if this is recommended!). Expect this part to take a while and don’t rush.
6. The sealing strips for the back should be pushed down bit by bit with the wooden tool. Cut with scissors when you reach the end of the gutter. Check that the back still closes properly.
7. Jon includes advice for Nikon FMs, which should be fairly generic. I found his recommendation of 3/32” foam for the mirror damper a little thick in practice compared to the original stuff, although I’m sure it will work OK - 1/16” is probably a closer width though. I considered using the neoprene foam instead, but thought it might be too firm.
8. Measure or guesstimate the size of the new foam and cut it out using the knife and a good ruler - a steel ruler shaped for safe holding is probably the best choice. Grip the new piece gently in a pair of tweezers (the adhesive will be sufficient to keep it on) while positioning it, before using the wooden tool to press it down as you remove the tweezers.
9. Clean any crud away from the focusing screen and mirror using a clean cotton bud - be very gentle. The bud should pick any bits up. (While you’re at it, clean the viewfinder externally with a bud too.)
10. Check the camera operation afterwards, and don’t use the first roll of film for anything important. Results TBC!

Other bubbles * Precise seal instructions for specific camera models from Jon Goodman. * Replacing deteriorated foam from the Medium Format digests (applies to 35mm too). * Micro-Tools also sells foam kits.