dry mounting question


Aug 6, 2004
Davidson, NC
I am still have some trouble using UMS dry mount paste with my vacuum press, posters and foam board. I am still getting some bubbles and bowing of the foam board. Should I be applying a more generous amount of paste? I almost get the impression that I am not using enough paste rather than to little. Any advice would be appreciated.
The bowing of the foamcore board comes from the expansion of the paper surface from all the moisture you are adding to it. In the past we would 'counter mount' paper to the reverse side of the board to balance out the warp age. You will not see this when using spray mount adhesives. I use the new 3M ProSpray system and love it. All of the problems you are experiencing will go away with that system.
Let's check terminology...

Dry mounting generally refers to use of heat-activated tissue or film with mechanical pressure (dry mount press) or vacuum pressure. The bond actually occurs during cooling, so the assembly must cool under weight.

Wet mounting generally refers to use of a water-based paste, something like wallpaper paste. (I think this is the process you're talking about.) Wet mounting is done cold -- no heat -- while the paste dries under weight or vacuum pressure. Vacuum is particularly good for wet mounting because the vacuum also dehumidifies, and speeds up the drying process.

Bowed foam center board usually indicates too much paste is being applied. Only a very thin film of paste is needed -- more is not better. I often apply the paste with a nearly-dry paint roller, and then blot away the excess with a piece of Kraft paper before laying the poster on it & slipping it into the vacuum press. All you need is a tacky-to-the-touch coating of paste.

If you have bubbles, maybe there's a pressure problem with your vacuum press. Have you verified that you have full vacuum with pieces of that size & thickness?

If your mount package is so large or thick that air is trapped under it & can't get to the vacuum ports, then you could have full vacuum, with plenty of pressure around the perimeter, and still have inadequate pressure in the center.

In any case, the problem almost certainly is not the paste. Wet mounting paste is a pretty simple concoction, chemically, and is not prone to inconsistent bonding.
Problem solved. The bloting made a big difference, no bowing, no bubbles. I am also inclined to believe that mounting board would probably be more forgiving than foam board as it is less likely to bow? I got a perfect mount on a 30 x 42 inch map that had been folded and creased.

Thanks again