OHP film drying tips?

[MurrayMinchin]

Got any tips for speed drying OHP film? Placing a fresh one before a fan still seems 'milky' in the dense areas an hour after printing it.

Thanks in advance.

 

[koraks]

I blast it with a hairdryer. Works OK. If high-density areas don't dry evenly, I take it as a sign that ink load is to high and adjust the parameters.
Just letting the sheet sit around for some time also does the trick, but sometimes we're in a hurry, eh?

Btw, inkjet prints tend to shift density (a little) as they cure. I think this effect drops away asymptotically after a day or two. There's a test somewhere online including density plots after several intervals to illustrate the issue. See also here: https://forums.piezography.com/t/ink-curing/733/4 which mentions that exposing the film to strong UV can also help 'cure' the print. IDK as I've not tested it specifically.
This 'dry-down effect' can be an issue if you're trying to linearize a process and/or run into unpredictable results. Of course, the phenomenon will be the strongest in the highlights, where they tend to matter the most...

 

[fgorga]

Btw, inkjet prints tend to shift density (a little) as they cure. I think this effect drops away asymptotically after a day or two. There's a test somewhere online including density plots after several intervals to illustrate the issue.

I have also read this somewhere but can not put my hands on the reference... arrgh!

My practice is to let negatives 'rest' for about 24 hours before using them for the first time.

In other words, if I print a negative in one morning I would use it until the following afternoon or if I print a negative in the afternoon, I'll wait until the following evening to use it. On rare occasion, I'll print a negative in the evening and use it the following afternoon or evening. Thus the wiggle word 'about' in the sentence above this paragraph!

See also here: https://forums.piezography.com/t/ink-curing/733/4 which mentions that exposing the film to strong UV can also help 'cure' the print. IDK as I've not tested it specifically.

I wonder if this holds for OEM inks as well as the Piezography ones.

This 'dry-down effect' can be an issue if you're trying to linearize a process and/or run into unpredictable results. Of course, the phenomenon will be the strongest in the highlights, where they tend to matter the most...

Agreed.

The wait is definitely irksome when working out a curve. However, short cuts may lead to less than optimal results. If accelerated drying at this step causes visible differences in the final print is anyone's guess. I've not seen results of any testing.

 

[MurrayMinchin]

I blast it with a hairdryer. Works OK. If high-density areas don't dry evenly, I take it as a sign that ink load is to high and adjust the parameters.
Just letting the sheet sit around for some time also does the trick, but sometimes we're in a hurry, eh?

Btw, inkjet prints tend to shift density (a little) as they cure. I think this effect drops away asymptotically after a day or two. There's a test somewhere online including density plots after several intervals to illustrate the issue. See also here: https://forums.piezography.com/t/ink-curing/733/4 which mentions that exposing the film to strong UV can also help 'cure' the print. IDK as I've not tested it specifically.
This 'dry-down effect' can be an issue if you're trying to linearize a process and/or run into unpredictable results. Of course, the phenomenon will be the strongest in the highlights, where they tend to matter the most...

Thanks. The bit at the bottom I put in large bold type probably had me going in circles more than once!

I've been making two 5x7's on each 8.5x11 sheet. My usual procedure has been to make a negative, take it into the dim room, coat a sheet of Kozo/gampi, let it dry for 1/2 hour with a fan blowing over both of them then make the exposure.

Yesterday I made a new negative on a sheet of OHP film with an older, fully cured negative on it. After the half hour, I picked up the dry paper and OHP film, then noticed the densest areas on the new negative were 'creamier' (on the reverse side) than the dense areas of the older negative.

This would be seen by the paper as additional density, yes?

Have had todays negative under the fan for an hour, then popped it into the UV exposure unit for 15 minutes. After that I'll coat a piece of paper and put both under the fan for half an hour and see what happens. Your use of a warm hairdryer would probably speed things along even more.

Ink load isn't the issue...using an Epson P600 on the Epson ABW (Light ink load) setting.

 

[MurrayMinchin]

...My practice is to let negatives 'rest' for about 24 hours before using them for the first time...

...The wait is definitely irksome when working out a curve. However, short cuts may lead to less than optimal results. If accelerated drying at this step causes visible differences in the final print is anyone's guess. I've not seen results of any testing.

Good points.

Maybe I should edit and print negatives in the evenings, then put them in a warm spot with moving air overnight. Still, would like to find a faster drying method for those spontaneous-revelation-must-make-another-negative-now moments.

 

[koraks]

This would be seen by the paper as additional density, yes?

Not necessarily; a difference in appearance of reflective density between two otherwise identical prints may (and likely will) correlate with a difference in transmissive density. But it's also conceivable that the drying rate results in reflective density differences that don't show up very clearly as transmissive density differences.
It's a bit of a minefield. You'd have to measure or compare prints to be sure.

 

[MurrayMinchin]

Not necessarily; a difference in appearance of reflective density between two otherwise identical prints may (and likely will) correlate with a difference in transmissive density. But it's also conceivable that the drying rate results in reflective density differences that don't show up very clearly as transmissive density differences.
It's a bit of a minefield. You'd have to measure or compare prints to be sure.

Probably best to ensure dryness thereby avoiding at least one landmine.

 

[koraks]

Yes, that's for sure.