Heat Press Troubleshooting

[Michael W]

Hoping for some tips on how to get around a problem. I'm using a heat press to flatten fibre prints - there are sixty of them, 16x20 inches, Ilford MGWT. The prints were air dried and are reasonably curly so we want to flatten them. Using correct procedure with the heat press, most of them are coming out fine. However there are about fifteen prints that are quite wavy along the short edges. When we put these through the press they came out with obvious cracks along those edges. We stopped after this happened to two prints, but now have the dilemma of how to proceed. The only thing I can think of is to rewash the prints until hopefully they lose the wave, then dry them and hope they end up in a state that enables them to go through the press OK. I'm just wondering if anyone else has encountered this scenario and if there are any known solutions. Thanks.

[Andrew Tymon]

I would rewash them and dry them slowly. Prints tend to curl if they are dried too fast, they emulsion side tends to dry quicker hence the curl. You could also dry them pegged back to back on a clothesline. Are you using drying racks?

[Erik Larsen]

You might try some steam from a tea kettle on the back of the print to relax the paper in the curly edges. Then stick back in the press when the moisture from the steam is dry enough to not cause problems in the press.

[bob carnie]

To add to Erik's response

You will need to raise the humidity in the mounting room as this is a known issue with low humidity conditions... I hate mounting hot prints in the winter as its really dry , so we pump up to about 50% with a portable room humidifier and it does the trick.

[Michael W]

Thanks for the replies thus far.
It is pretty humid here in Sydney, but the prints are very dry, having been made last December.
They were dried on racks, face up, which is how I will dry them again.
Can't use pegs as the image goes right to the edge of the paper, so can't risk any marks.
I will also test one with steam.

[Mrportr8]

The key to flattening large prints is to do it slowly, in stages. You can start by placing a board (with a lyer of paper on them as cushion & 1/2" (13mm) plywood, 1/4" (6mm) masonite, etc.) over them and slowly add a couple of books after a day or two. Then place them in the press for a few minutes with a light pressure. Remove them and let them cool face down on a clean surface under the same board you used previously. Then repeat the process and after about three or four sessions in the press with light pressure do one final run at full pressure. Another option would be to re-wet them with a flattening agent which will help to stabilize them.

[Renato Tonelli]

You may want to flatten them soon after the have dried or place them under some weight until you can get to them.
I have had a similar experience. Leaving a generous white border also helps - trim 2cm all around after flattening.

[Michael W]

The test print that I rewashed on Saturday had dried quite flat when I returned on Monday. Flattened easily in the heat press, so that's good news that a wash can get rid of the waviness. This afternoon I have rewashed the remaining wavy prints and will check them tomorrow.

[Michael W]

Yeah, in retrospect we wished that we had bought 20x24 and then trimmed to 16x20, but we didn't anticipate this problem.
Another thing that is interesting is that the same paper is drying quite flat in the current hot and humid weather, but dried really wavy a month ago. It must have been a drier heat then.
I have very little experience with heat presses so I'm learning a lot of new stuff.

You may want to flatten them soon after the have dried or place them under some weight until you can get to them.
I have had a similar experience. Leaving a generous white border also helps - trim 2cm all around after flattening.

[don mishler]

"They were dried on racks, face up"

I was taught to dry fiber prints face down. Since the paper wants to curl to the emulsion side the weight of the paper reduces the curl. It makes a big difference. Of course you want to keep your screens clean.


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[Steve Goldstein]

Another thing that is interesting is that the same paper is drying quite flat in the current hot and humid weather, but dried really wavy a month ago. It must have been a drier heat then.

I've noticed that too. Where I live we have strong seasons - prints always dry much flatter in summer when the humidity is higher, and tend to have a lot of waviness during winter when the central heating is on and the indoor humidity is extremely low. I used to take the drying screens into the bedroom where we run a humidifier in winter, but this risks prints getting stepped on in the dark.

What works for me, and is better for marital relations, is "dummy" prints. I use Kostiner screens, which are stackable, so in winter I usually put the good prints on the lower screen(s) and some throwaways (fully washed, of course) on the top-most screen. This slows down the drying rate of the prints lower down and reduces their curl.

I also dry my prints face-down so they curve less, as Don Mishler describes. I usually wipe the screens with a damp cloth immediately before use to remove dust that might otherwise decide to attach itself to the image, and the screens get an occasional gentle cleaning in the shower as well.

[Michael Rosenberg]

Drying the prints face up may be the issue. It will add to the curl of the paper greatly. Control humidity in the room to about 50%; both when drying the print and after removing the prints from the dry mount press after mounting. After mounting put them under a weight both to allow the glue to solidify and for humidity equilibration. If you are printing to the edge of the paper how are you trimming the mounting tissue?? The problem may be that the tissue is not to the edge. Also you may get cracks at the edge because the emulsion is more fragile on the edge.

Mike

[Dave Ogle]

THIS WORKS. I DO THIS.
I had the same problem. I live in midwest. Summer - humid. Winter - dry.
I was air drying on screens. Face down. was ok.
winter came and switched brands of paper.....
lots of curl.

have carpet in work room.
put screens on carpet.
squegee prints front and back
prints face down on screens.
cover with 2 layers of towels. maybe 1 layer might work.
leave over night.
Next - hot press
175*
have a piece of mat board in press.
put print in between a piece of paper and mat board.
bring down press on print lightly for a few seconds, but don't lock it down
rotate, again lightly press
it should start to flatten now.
(lightly press and rotate are important, maybe several times)
flip it over, press again.
if it look pretty flat when you flipped it, you can lock the press down
not long, 15 - 20 seconds
should be flat
place on hard surface.
put something on top of print, of at least same size or bigger and some weight on top that
you can stack 10 or so prints. let cool. a few hours under weight.
Dave

[Michael W]

Unfortunately this is being done in a public darkroom where we have no control over humidity or other aspects. I don't trust the screens to be clean, hence drying face up to avoid other problems. We are not using the heat press to dry mount, just to flatten the prints so they can be bonded to aluminium at a framing place. I think they use adhesive rather than heat. The aim is to deliver them prints as flat as possible.
It's like a sauna in Sydney today, hopefully that helps the non-wavy drying. It's also a bit of a big job because there are sixty to deal with.


Drying the prints face up may be the issue. It will add to the curl of the paper greatly. Control humidity in the room to about 50%; both when drying the print and after removing the prints from the dry mount press after mounting. After mounting put them under a weight both to allow the glue to solidify and for humidity equilibration. If you are printing to the edge of the paper how are you trimming the mounting tissue?? The problem may be that the tissue is not to the edge. Also you may get cracks at the edge because the emulsion is more fragile on the edge.

Mike

[bob carnie]

Unfortunately this is being done in a public darkroom where we have no control over humidity or other aspects. I don't trust the screens to be clean, hence drying face up to avoid other problems. We are not using the heat press to dry mount, just to flatten the prints so they can be bonded to aluminium at a framing place. I think they use adhesive rather than heat. The aim is to deliver them prints as flat as possible.
It's like a sauna in Sydney today, hopefully that helps the non-wavy drying. It's also a bit of a big job because there are sixty to deal with.

You are asking for a lot of whoopass if your framer is cold mounting fibre prints with adhesive rather than hot mounting... just sayin.