Longest possible exposure time for collodion?

[likeoras]

Hey to all of the wet plate shooters here,

In your experience, what's the longest exposure time you've been able to milk out of a plate before it gets too dry?

Just curious if people's experiences are similar or varying (and why!).

Thanks!

[Jason Greenberg Motamedi]

Depends on the weather--in hot dry desert like conditions I found that after two minutes exposure (not counting time in the holder, before and after exposure) my plates were showing scaling and uneven exposure. In the cool pacific northwest I have gone up to five minutes with no signs. Of course, plate size, camera size, and the construction of your holder are also important factors.

[Joe Smigiel]

It also depends on the formula. Collodion iodized with sodium salts will dessicate quickly. I believe ether will evaporate quicker than ethanol due to the latter's water content and that could affect the rate.

Some folks put a damp fabric on the back of the plate to extend the useful working time. Supposedly that keeps the humidity higher in the holder and gives a bigger window.

The longest I've gone is probably around 6 minutes on a cool (68F/20C) day. But with sodium salts I also got drying marks at around 2 minutes under similar conditions.

Some people have reported doing up to 15 minutes or longer in winter.