Why is this Happening?

[Joe O'Hara]

Hi, ASA1000. Reading about your processing steps, it seems a bit strange to me that you flatten your prints for four minutes at 165 deg F in a press, and allow them to cool between two sheets of glass. I have never heard of allowing prints to dry under glass, which is completely impermeable to moisture, and seems likely to lead to different amounts of retained moisture in the paper in the edges compared to the center--whether it is from the middle trying to get out, or from the environment trying to get in.

You do not tell us what is between the heated platen of the press and your prints. That could be important.

I will tell you what I do, and I have no problem with wavy edges or getting my prints flat when unmounted. It is this:

Washed prints, after being hung by the corner by a clip for a few minutes (basically until I have the last print from the washer hung up), are then put image-side down on a clean piece of plex and wiped with a clean cellulose sponge. The mopped-off print is then placed face-up on the drying screen and mopped on the emulsion side with a clean cellulose sponge, then flipped over image side down and allowed to dry overnight, or longer as the RH demands and the print seems uniformly dry and "crisp" to the touch.

When it is time to flatten them, they go face-down on a clean piece of archival cotton rag matte board in the press, with four or five sheets of archival "interleaving paper" on top of it. The press is heated to my usual 190 deg F setting (checked with a thermometer). The press is closed for 30 seconds, and then the print removed. Note: The matte board and cotton rag interleaving papers have been thoroughly cooked beforehand and allowed to dry with the press open for a minute or so before the first print is done.

The prints treated this way come out perfectly flat, with a slight curl to them that relaxes a bit in time. You could mount them with corners and they would be as flat as they would be dry-mounted.

BTW I have gotten the same results if I just let the prints dry hanging from the corner and flatten them right from there, but I don't usually do that because they tend to dry with a random curl in them that can be a little challenging to deal with in the press.

When I (years back) would see curly edges, it was because the print had too much moisture in it that I tried to cook out of it too quickly. The different rates of shrinkage got "frozen in" in the form of edge ripples. It is a sign that the drying process has occurred unevenly. Check the temperature inside your press with a digital cooking thermometer, provide pre-dried absorptive materials in the press, and lose the glass plates, you don't need them.

I should say that I do not know of any process that leads to a "perfectly", geometrically flat print. The procedure that I use yields prints with a gentle uniform curve to them (BTW I use Ilford MG Fiber papers), which I find unobtrusive to detailed examination or subsequent dry-mounting.

[ASA1000]

Hmm. I started seeing this when I moved to ultra-dry Tucson. At first I thought it was my new (old) dry-mount press. Then I was given another press, and the issue (mostly) went away. So I think it's mostly humidity and then a matter of mounting technique. But I'm not certain of that.
One change I've made has been to dry my prints between two screens, instead of on top of one, in an attempt to reduce curling. That seems to help.

I never thought of it as a function of what part of the master roll the paper sheets came from. Those are very wide... It seems unlikely, based on the many hundreds of prints that I've flattened, in many different presses, over the decades. And the many brands and types of papers that I've used. But who knows?

Thanks Mark. 'Who Knows" is right, but I'm looking into it! Perhaps this is a result of Global Warming ? Bwahaaaaha!!
I've trimmed the wrinkles off a few prints and I'm going to rewash one and re-dry it. Then I'll see if it reappears on that same sheet, but yes, I too think humidity IS involved. My stuff air drys in about 3 hours in my basement, which, from previous experience, is awfully quick.My last darkroom was in Santa Fe and I didn't have this problem, but I was printing on Gallery, back then.
I like the between-two-screens approach. I'm going to try that.

[d.s.]

Adjust the black knobs so that the platen is parallel to the cushion in the bottom, and it takes some effort to lock the press. Equal pressure, equal heat, equal drying ??

[MartinP]

In addition to my post far above somewhere, I am one of those who does not have a drymount press, nor room for one even if it was a gift. For larger prints I give an extra 1/4" border all round, then dry them on a glass door and some bits of polycarb glazing, fastened down with the tape used by water-colour painters to hold their paper during the shrinking process. They are pretty flat when they come off the support and trimming off the gummed-tape (not parcel-tape remember) relaxes the edges too.

[Ulophot]

Michael, two things. One possibility of course is more humidity, but that may not be practical in your set-up. The second, which I'll simply report, since I haven't tried it and it surprised me: Alan Ross, former Ansel A assistant, replied to a general question about this issue on a conference call yesterday. He said that feeding the print bit by it into the dry mount press, pressing each section before moving the print further in, solved the problem for him. Whether that would work for your anomalous problem I have no idea. One a wave is turned to a wrinkle under pressure, it won't come out.

Good luck, whatever method you try.

[ASA1000]

I'll answer the questions:
Joe: I had been using an old silicone cover sheet on top of the print and Kraft paper below.
d.s: Yes, I noticed the patten was not level. I think it must have gotten tweaked in the two move, so I spent a while loosening everything up and readjusting it. In the process I noticed the pad was squashed down on the side the platen was down on, I've flipped the pad and shimmed the low side so it's all level now.

I do think that prints are drying too fast. In other darkrooms it was always overnight on a screen, but here, prints are dry to the touch in a little over three hours. Yesterday I tried putting them in the press at 3 hours, between two sheets of heavy archival watercolor paper, 200 degrees for 45 seconds, then open the press to let it air out, and then close for another 30 seconds (this is the procedure Seal recommended with the press in their instructions).First try, I put four prints in the press and two of the prints were still moist enough in the middle to stick to the overlay, so I went up to 3:30 air dry and then in the press and that was good. Then the prints went inbetween glass to cool and then into a storage box. They were all still flat this morning.

Conclusions:
I think 'too hot in the press' was especially a problem in the dry humidity here. I need to get a hygrometer to see what it actually is in the basement. Too long in the press was a problem too.

Blotting the print - (I read back in Ansel's Print book, he liked a sponge, too) is key. At first I squeezed them but that still left too much spotty moisture, so now I am blotting with a towel but I have to use a totally dry section of the two towels each time. If I use the same spot I can see the print dry differently Blotting helps and you can see it as the prints dry- they dry more evenly and the corners curl up more uniformly as they dry (not the wavy problem, just natural curling while drying to flat)
I haven't tried drying on a screen with another screen on top but that seems like a good idea as well.

The un-level platen had to have uneven temperature and pressure. This must have had some effect. Today I'm re-wetting four previously flat prints and I am going to re dry them, marking the positions and orientation in the press.

I think the key is going to be either more humidity or catching the air drying at just the right time before going to flattening in the press.

I've been taking video of the drying process. I'll put something together so you can see what's happening.
Thank you all!!

[Cor]

One thing to add: (that's how I learned it, and might not be useful to you anyway, since humidity at my place is (almost) never below 60%) after the dry mount press, the hot and flat paper is moved swiftly to a glass plate and heavy plate of aluminum on top: I have the aluminum plate at 45 degrees, and let it fall on the paper. This "chock" is supposed to keep the paper flat.

Good luck,

Cor

[ASA1000]

One thing to add: (that's how I learned it, and might not be useful to you anyway, since humidity at my place is (almost) never below 60%) after the dry mount press, the hot and flat paper is moved swiftly to a glass plate and heavy plate of aluminum on top: I have the aluminum plate at 45 degrees, and let it fall on the paper. This "chock" is supposed to keep the paper flat.

Good luck,

Cor

I'm going from press to between heavy glass now, ...... but the 'shock' is something new

[LabRat]

Wrinkles in dried prints usually come from uneven wetting/drying during process where areas are more/less "wet" or dry unevenly which changes the sizing of the base... This causes areas to expand more than others, and when flattened, can leave waves and wrinkles where expanded areas have nowhere to go... Or from excessive wetting where areas become more saturated than others and can changing sizing of base...

Check to make sure that the edges are completely submerged during every step of the process, and well wiped and dry evenly and fully before flattening... Make sure prints stay fully immersed while in the wash and without bubbles or excessive flow while washing... And prints need to be thoroughly dry (beyond even feeling dry) where there can be differing moisture content that can press unevenly with heat applied...

Try waiting another day or two drying in air before flattening...

Good luck!!!

Steve K

[ASA1000]

Wrinkles in dried prints usually come from uneven wetting/drying during process where areas are more/less "wet" or dry unevenly which changes the sizing of the base... This causes areas to expand more than others, and when flattened, can leave waves and wrinkles where expanded areas have nowhere to go... Or from excessive wetting where areas become more saturated than others and can changing sizing of base...

Check to make sure that the edges are completely submerged during every step of the process, and well wiped and dry evenly and fully before flattening... Make sure prints stay fully immersed while in the wash and without bubbles or excessive flow while washing... And prints need to be thoroughly dry (beyond even feeling dry) where there can be differing moisture content that can press unevenly with heat applied...

Try waiting another day or two drying in air before flattening...

Good luck!!!

Steve K

I bought a hygrometer and I'm at 20% humidity. It's definitely more moisture in one spot than another. I agree my problem is in the drying, but I think they are drying too fast and curling too 'hard'.. I'm watching the prints every few minutes as they dry and the edges dry first and then the corners begin to bend up. If all is good, the corners will lay down as the print dries and all is good, but sometimes a bubble appears in the middle of the print, as it begins to dry and after the edges curl up. That bubble is a still moist spot and as it dries it puts its own bends in the short edges of the print. It's as if there were a wood grain going lengthwise in the print that directs the wrinkle. Maybe it's in the paper? I have found I can 'massage' the wrinkles out in a warm water bath and re-dry the prints flatter but not perfectly flat.
Yesterday I took 8 prints off the screen at 3 hrs and 30 minutes and cycled them in the press 45 sec, air and then another 30sec in the press and all were flat and normal.
If I get through today unscathed, I think I might be on the right track.
thx!