Mat board curving after pressing

Finally broke down and got a dry mount press. The first one I did looked great for a few days then it curved. I put the mat in the press few a minute or so the get any moisture out. Then did my thing. Is this just a trial and error thing or did I miss something?
From my woodworking days I know if you put veneer on one side you need to put veneer on the other side to keep everything in balance. Pulling equally from both sides.

Thanks

I think you hit the nail on the head. This website below refers to it as counter mounting. For sure you want to make sure that your print is really, really dry before dry mounting it. Like maybe a week if you are in a high humidity area. I had the same warping issue using spray on adhesive to mount large photos to foam board (I know, I know), and resolved it by gluing the foam board to Masonite. In New Mexico I never had warping, but I had tons of dust. In Florida I have no dust, but things warp. You could use something similar to a wooden frame canvas stretcher arrangement too. Anything to give you more support than just the mat board. In any case, this link has some interesting info.

http://www.designsinkart.com/library/M-KnowingWhenToCountermount199908.htm

It happens often when your photo has more shrinkage than the matboard, especially when using single-weight board. Try drying your prints before mounting them.

Did you mean by "did my thing", dry mounting? After pressing, did you leave the completed product under glass or some other smooth surface long enough to completely cool?

What I usually do is, I do "my thing" and as soon as it's done, take it out of the press, rush over to my living room where clean glass top table is, place it, and put another thick glass over it. Let it cool down for about 30 minutes.

If I hurry and don't do full 30 minutes, it tends to curl in day or two.

Like tkamiya I would like to understand what you were doing:

- mounting a print to carton? If yes, was it a fiber paper print or PE?

- flattening a fiber print?

- how large was your print / carton?

I use two drymounting presses, mostly to flatten fiber prints. A Büscher 50X60cm (20X24) and a Seal 210 40X50cm (16X24). But I have also mounted prints to carton.

For both dry mounting and flattening, it is essential that after pressing you "rest" your print for at least a night. It means you put the print between acid free blotters (a stack of cartons, like Hahnemühle 921) and you leave it sit 10 hours for sure.

Then, equally essential, you should trim all four sides of the print, or of the mounted print. In doing so you cut away the tension of the paper. Just half a cm is enough.

I do not like dry mounting prints very much. But flattening is great when you use the press. It is a little complicated though, because there are different parameters at play:

- the tension of you press (should be adjustable)
- the temperature you use
- the pressing time
- as said before the yes/no humidity
- the type of photo paper (glossy, mat, etc)
- pressing the print face down from the heated plate, or not . . .

You will need to experiment, obviously

You need to keep them under weight while they cool. I use a huge piece of thick plate glass. Then you need to keep the matted prints flat
under weight basically forever thereafter, whether stacked in portfolio boxes, stacked upon each other in drawers, or held flat in a picture frame sandwich. Once the humidity goes up, the mounting board will absorb moisture and something will bow. And if you don't pre-dry your board just before mounting, the bond is likely to fail while the moisture is trying to escape during the pressing phase. Basic technique. Some people might work in desert climates which seemingly simply this; but once they ship a print elsewhere, it will still bow due to a
new humidity level. Countermounting is rarely used in drymounting, because bowing is a relatively minor nuisance, but routinely used in wet mounting, which has a much bigger problem in terms of predictable bowing.

Sorry about detail. Sometimes I give way to much and other times not nearly enough.

In this case I used a 8x10 picture and the mat was a 14"x14" piece of leftover mat.

- I matted this picture in May, other projects came up so I had to drop the picture mounting for awhile. - As for humidity I can't say. In May the AC would have been running but that's all I have got.
- I used a mat finish RC print, tacked the tissue to the print. Print was made in December.
- Heated the mat board for a minute or so to dry any moisture. Wasn't aware mat board had grain.
- Placed the picture on the mat board, picture face up, put silicon paper below mat and above picture and closed the press. I don't remember the temperature or time. My guess would be the temp was in the 180 to 190 range and the time 45 second to a minute.
- When I removed the picture I rolled the mat in reverse to make sure it was glued properly, which it was. No loses edges or corners.
- Placed it under a piece of 3/4" plywood with 12 -15 pound weight on the plywood. Don't remember how log I left it to cool.

Everything came out great and I set the picture on a table. I looked at it a couple of weeks ago and the mat is curved toward the picture side. The picture is still glued to the mat board on all edges.

I have gone to art show and artist have 11x14 pictures mounted on 16x20 mat and flat as a board. How do they accomplish that? Leave them under weight until the show?

My goal is to participate in a show with pictures mounted on backing boards with the appropriate window mat hinged. And be flat.

That was my first try and I was so pleased until the curl set in. I want to try some more but need a little direction on what to try next.

Any gallery which simply pins bare mats to the wall is an Oakie outfit to begin with, in my opinion. The boards will still warp given any
significant change in humidity if they aren't framed. They're just gambling on that not happening during the duration of the showing. I leave
my day's worth of drymounted prints stacked under the heavy glass for quite awhile. Then into stacked storage. These behave pretty well after that, but not necessarily forever apart from controlled parameters. Your storage conditions should not have wild swings in humidity,
which is bad for other reasons, including mold risk. Print paper, drymount tissue, and the board all have different coefficients of expansion and contraction. And don't use plywood as a weight. It's got nasty things in it like wood acid and generally formaldehyde glue that are really bad for photographic and paper permanence.

I'd use the link momus provided with reference to counter mounting.

I had issues with warping but then switched to a four ply matboard which seemed to fix the problem. I also did the rest thing other users spoke about after pressing the mounted print.

Different brands of board also differ somewhat in this respect. Helps to experiment a bit.