Air Dried Wet Plate Collodion Varnish Development

Air Dried Wet Plate Collodion Varnish Development

Posted by Brian Cuyler on Apr 2nd 2020

Many people hate varnishing and feel that it is the most difficult part of the whole wet plate process.  There are several reasons for this.  One culprit contributing to this is varnish that is too thick which makes it hard to flow over the plate, drain and clear the heavy edge.  To help this, UVP varnishes were formulated to flow and drain as easily as possible.  Regardless of the resin, sandarac or shellac, the basic formula is resin, 95% ethanol, and lavender oil.  This type of varnish dates back to when this process was being used in the 1850's and 60's, and has proven to be durable enough to last for 150+ years. This mixture can give excellent results but requires, coating, draining and heating in  almost ideal conditions to get a beautifully varnished plate.  If the plate is drained, and the edges blotted too long, the varnish will begin to dry and will crate matte and mottled areas in the varnish.  This makes technique integral to getting a good finish.  To help with this stressful part this an amazing photographic process, I wanted to make an easy to use varnish using the same basic ingredients, but with a long open time before heating.  Or, even a varnish that can dry at room temperature.   

To do this several variations were created using a base resin of shellac with a small amount of sandarac in 95% ethanol. As with most of the UVP varnishes, it was carbon treated to remove some of the natural color.  Several solvent and lavender oil variations were created and tested.  

I've found over the years that I can varnish blank uncoated plates to get an idea of how well the varnish performs.  Using these I did variations of heat, no heat and 1, min, 2 min, 3 min before heating.  I also did variations of where the plate was heated before varnishing and with the plate at room temperature.  

This is what a plate looks like with no lavender oil that is air dried with no heat.

Here is one of the variations, no heat & air dried.

By changing the solvent from only 95% ethanol to a blend of 95% ethanol and slower evaporating alcohols it is possible to make a varnish with the same resins and lavender oil that has a long open time that can be air dried if desired.  

Not only does this make it easier to varnish everyday plates, but for those making ULF plates this is a game changer.  Varnishing ULF plates is a hectic array of flowing, draining, blotting, then finding some way to heat the plate. Usually the finished result is less than perfect.  An air died varnish allows for a a ULF plate to be vanished with the same results obtainable on smaller plates.   

Here is an exposed plate that was varnished and left to air dry for about 15 minutes. 

Conditions Tested:

70°F 50% RH - Air Dry OK

52°F, 86% RH - Air Dry OK

65°F, 70% RH - Air Dry OK

52°F, 90% RH - Air Dry Poor -  Fine if heated after coating

72°F, 60% RH, Full Sun - Air Dry OK

Next steps:

Test with old red collodion to see how aggressive it is.

Test under high ambient temperatures and high humidity.

Stay tuned,

Brian