On 8 Sep, 18:32, Bill wrote:

All this talk of fuming ammonia sounds scary, but I'll look it up.

You make a big box / tent and put a tray in the bottom of it with some
strong domestic cleaning ammonia in it (doesn't have to be .880,
doesn't need to come from the mythical draughtsman's suppliers). Then
wait 24 hours. I usually want to fiddle after about 12 hours, so I
have a look inside and often re-arrange bits so that nothing is
getting shaded.

For small pieces, big Tupperware is enough. For most work, I use a
Perspex "coffin" that used to be a piece of terrifying lab
electrophoresis kit (keeping the chemists away from the killervolt
supplies). Wardrobes use a custom-made tent out of polythene sheet,
beansticks and parcel tape.

Don't spill the ammonia. Direct liquid contact goes black.

Watch out for sapwood. The ammonia reacts with tannins in the
heartwood alone and sapwood stays pale (like the crap I saw for sale
in Habitat last weekend).

I wear a full-face mask, but it's not essential.

also been scouring the internet without finding where to buy "Patina"
near Liverpool.

Langlow make it (in Speke, I believe). I'd given up hope of seeing it
again until I walked into Newlands in Ormskirk recently and they had
plenty.