How to filter sensitizers?

[MurrayMinchin]

Hi there,

My Argyrotype sensitizer is over a year old and is still performing. I'd like to filter it in case any gritty bits have formed at the bottom of the bottle.

What material is recommended for filtering alt process sensitizers?

 

[koraks]

Coffee filters generally work. If you're of the more fancy persuasion, try Whatman filter papers. Some coffee filters can contaminate the sensitizer; proper filter papers can be expected to be clean.

 

[MurrayMinchin]

Coffee filters generally work. If you're of the more fancy persuasion, try Whatman filter papers. Some coffee filters can contaminate the sensitizer; proper filter papers can be expected to be clean.

I've heard coffee filters can vary quite a bit in quality. Thanks for the Whatman tip

 

[Ian Leake]

I use Whatman #1 filter paper (11 µm) for rough filtering, #6 paper (3µm) for fine filtering, and 0.45µm autovial filters for extreme filtering.

 

[fgorga]

I would use lab grade filter paper. Whatman #1 (or its equivalent is most generally useful.

Coffee filters can have impurities with adverse effects... there was a thread here not too long ago (I think, but can not find it) where someone traced their alt process problem to the use of coffee filters.

Here is a video on how to fold filter paper to fit a funnel: . I have use the second method shown for a very long time (50+ years... egad!).

 

[MurrayMinchin]

I use Whatman #1 filter paper (11 µm) for rough filtering, #6 paper (3µm) for fine filtering, and 0.45µm autovial filters for extreme filtering.

Thanks. Number 1 should do the trick.

 

[MurrayMinchin]

I would use lab grade filter paper. Whatman #1 (or its equivalent is most generally useful.

Coffee filters can have impurities with adverse effects... there was a thread here not too long ago (I think, but can not find it) where someone traced their alt process problem to the use of coffee filters.

Yup, the coffee filter thing must have been a real head scratcher...want to avoid that for sure!

 

[koraks]

there was a thread here not too long ago (I think, but can not find it) where someone traced their alt process problem to the use of coffee filter

Yeah, although then a later thread suggested more causes and the woods just got thicker. But I recall and I agree that some coffee filters may not work well. IIRC in that particular case the nicely bleached white ones proeuded problems and the plain unbleached brown ones didn't. The latter were very close or identical to the ones I've used many times. Btw, that was with cyanotype of memory serves, I think New cyano specifically.

Btw cotton pads or balls also work quite well for coarser filtering.

I prefer to make only as much chemistry as I can use up in a short period of time and avoid the whole thing.

 

[MurrayMinchin]

...I prefer to make only as much chemistry as I can use up in a short period of time and avoid the whole thing.

One of the things which appealed to me about the Argyrotype process was how long the sensitizer lasts.

Mike Ware states, "The solution should keep for several years. If it throws down a small amount of black precipitate, it should be re-filtered."

He also mentions using a Whatman #1 filter

https://www.mikeware.co.uk/downloads/ArgyroWork.pdf

 

[koraks]

The same is said about certain other sensitizers. A sensitizer that precipitates out a black powder is losing something, likely silver. I want the silver to be on the print, not in a filter.

 

[NedL]

For calotype sensitizers ( AgNO3 + acetic acid ) I use a cotton ball pressed into the spout of a plastic funnel. I haven't try kaolin, which is another way to trap larger particles and make them sink to the bottom of the container.