As I’ve worked in the wet plate collodion process, I’ve accumulated many images that show extreme effects of chemical reactions and accidents of the process.  Sometimes colder temperatures caused the developer not to flow properly.  In other instances, the collodion was too old and formed on the plate in a mottled way as it was poured.  Then there were also cases of silver nitrate flowing across the plate and leaving traces of movement while the plate was in the camera holder.  Finally, there were some plates that had contaminants on their surfaces — specks of dust, and such.  These are among my favorites.

In this YouTube video, Quinn Jacobson demonstrates the proper technique for protecting a collodion emulsion with a varnish consisting of gum sandarac, alcohol and oil of lavender.  If you watched the Sally Mann video (two posts back), you saw her scraping a collodion emulsion from one of her glass plates in the field.  Perhaps an initial pour did not go well and she wanted to recoat the plate; or she was not completely satisfied with an image and wanted to start over.  Collodion can be easily removed from an unvarnished plate.  Left unprotected, the emulsion will eventually begin to peel off and may completely disintegrate.  Varnishing is simply a way of ensuring the archival quality of the plate.