Designs Ink Publishing Article Archive and Reference Library
Articles by Chris A. Paschke, CPF GCF CMG
"TTPM…The Four Elements of Mounting"
In my January article "Adhesive Trends for 1992" I mentioned the four key elements to successful dry mounting as TIME, TEMPERATURE, PRESSURE and MOISTURE. Although this is geared more directly to heat-set tissues and films, the same should be respected in other mounting disciplines as well. Predictability is the hallmark of dry mounting. When repeatedly mounting items over and over again, the end product should turn out the same each time. Generally speaking if there is inconsistency with your dry mounting it may usually be tracked to one of the key elements being out of sync with the others.
It would be nice to be able to lay blame on the equipment, tissues or the manufacturer's lack of quality control, because then we could successfully avoid wearing the responsibility of problem mountings. Unfortunately, quite often it is our very own inconsistency or attention to details which gets us into trouble. Overused or wrinkled release papers, foam rubber with divots torn out and transferring strips of adhesive to the face of a newly mounted print are often key offenders in the graveyard of unsuccessful mountings, all of which may be tracked back to operator error.
The ratio of time, temperature, pressure and moisture (humidity) vary depending upon the mounting process, equipment and adhesive being used. The basics of wet, spray and pressure sensitive mounting follow the procedures to be outlined here, but at times also include the elements of "tack time" also called "open time" as well. This is the workable time allowed by the adhesive to position the print to be mounted as the solvent evaporates. Open times vary depending on the product so be familiar with its proper usage.
Application time also comes into play with wet and spray adhesives in that a good uniform coat of adhesive must be applied in order to quarantine good adhesion. Any areas which have begun to dry prior to mounting the art will not create a lasting bond. Although a basic bond will be created within the first hour, more permanent bonding will take 4-24 hours and should be done in an undisturbed area under pressure.
The time it takes to dry mount a project will vary depending upon the adhesive, substrate, size, temperature and item being mounted. As discussed in "Adhesive Trends for 1992" (PFM, January '92) tissues and films mount between 165-185F. The "dwell time" is the time remaining in the press to adequately heat all inert materials, activate the adhesive and create the bond. If a project is removed too soon for proper bonding it may be repositioned in the press for a second time. When taking this additional step a couple of important items need to be remembered. First, if left in the press for 2 minutes under the initial mounting in order to achieve an additional 1/2 minute of dwell time the project must remain in the press a total of 2-1/2 minutes the second time. Second, as a direct result of having to mount the project an additional 2-1/2 minutes you have now not been time and cost effective.
The important thing here is to match the proper time/temperature ratios. Since it is increasingly desirable to dry mount at lower temperatures the dwell times will become a little longer. Simply because a particular print may easily tolerate a higher temperature does not suggest turning up the temperature to cut down the time required to mount. This can be a risky endeavor and quite often you will be the one to lose. It is far better to work at lower temperatures with a slightly longer dwell time than to up the temperatures in an attempt to speed up the production process.
As already noted it is impossible to give the end all temperature to be used in every situation, for adhesives range from 150F to 225F. Individual tissues and pure adhesive films vary depending upon the item being mounted and its substrate, however common sense should help you consider the layers of board to be heated up for the required final mounting temperature to be obtained.
For example, an 11x14 piece of velour fabric being mounted onto foam board for a shadow box creation using pure adhesive film (Fusion 4000 or TM3) may be pressed at 185F for 2 minutes while an 11x14 4-ply mat board with 3 layers of art paper and a final 4-ply mat board (all appropriately layered with pure adhesive, to create a multiple striped bevel) may take the same 185F but for 6 minutes, maybe more. Quite simply there is more to heat up to adhesive activating temperature thus the dwell time is greater.
Honestly, it is best to establish a good average use temperature of about 180F which should meet most of your mounting needs. Don't regularly attempt to vary the press temperatures it is a source of frustration that is never needed.
Pressure is the force that squeezes the air from between the substrate, adhesive and print or photo being mounted. Uniform pressure is mandatory and in a mechanical press should be set according to the substrate being used. One of the great advantages to using a vacuum press is the conformity of the diaphragm (or rubber base) to totally conform the dimension of the variable substrates being used. Thus if mounting with a 4-ply mount board then immediately following with a 1/2" foam board and then 1/8" foam board, no adjustments need to be made to the press. If these variations were needed when using a mechanical press the lever arm would need to be adjusted each time to create proper pressure for adhesion.
Keep in mind the lever arm of a mechanical press should rest at 45 degrees to the table, with the substrate to be mounted inserted. Refer to your owner`s manual to determine locking nut and adjustment screw procedures on your individual mechanical press. It is suggested to adjust the press to the thickest, most used substrate (say 3/16" foam board) then by cutting shim boards the size of the masonite beneath the sponge pad, insert them as needed to accommodate for lesser thickness mount boards.
Proper, uniform pressure is a must and often may be the culprit when a good bond has not occurred. On the other hand, too much pressure may be detrimental also. When mounting an oversized poster in bites using a mechanical press, if the pressure is too great, indentations may appear on the finished foam board mount, as well as the press being more difficult to release. This will be addressed in an upcoming article on oversized mounts later this year.
Also, never overlook the need for pressure while cooling the once mounted artwork ("Adhesives", January 1992 and "Work Station", 1992). Once again removable adhesives bond under pressure once removed from the press.
All paper products and porous materials absorb moisture. When this moisture is heated in a press the steam-like vapors which develop may become trapped between the layers being mounted. Predrying the materials may greatly reduce the likelihood of this problem from occurring. In a mechanical press it is mandatory the substrate, print or fabric to be dried, yet in a vacuum press is only highly suggested. Predrying pulls the water moisture from the materials before the project comes in tact with any adhesive.
Brown absorbent Kraft-type paper is used as an inner envelope with a release paper outer envelope, the press is closed for 15-30 seconds. Repeat this process with the item to be mounted then proceed to mounting. Many non-porous materials such as Plexiglas need not be predried since they are unable to absorb moisture. Cibachromes should be kept from the press as much as possible since they contort to any texture they come in contact with when heat is applied, adhesive or no adhesive.
Perhaps the clay coated surface and inert core of standard foam board may not need to be predried, I personally feel it can't hurt. Once a routine procedure is established, such as weighting all projects that are removed from a dry mount press, a good habit should not be broken. Plus if using acid-free foam board the surface paper is much more porous and predrying is advised.
As mentioned earlier, the process of predrying is not "required" but rather "advised" when using a vacuum press. The very action of the vacuum sucking the air from the press pulls the moisture out with it. This step in conjunction with the automatic pressure adjustments of the rubber diaphragm make the hot/cold vacuum system very appealing.
Now that time, temperature, pressure and moisture have all been addressed, let's consider what might happen if any one of them is out of balance with the other three.
If large 2" air bubbles where appearing under a poster mounted to 3/16" foam board with a permanent breathable tissue core adhesive what might the problem be? Check the time/temperature ratio to verify the proper dwell time required, it may simply need a longer time in the press. Did you use a permanent or removable adhesive which may have required cooling and bonding under pressure once removed from the press. Also check the pressure to ensure the proper 45 degrees for the materials being mounted. Maybe you should have predried the print and board even if you are located in a very dry climate and generally don't predry foam board for it could be trapped moisture. It could also be the mount board chosen for the project. Some less expensive foam boards are better used as backing but not mounting because of their inconsistent paper bonding to the core which may separate under the stress of mounting.
All mounting problems should be trackable. By that I mean pick apart the elements of the mounting procedure and check all the steps. Somewhere along the line, the elements necessary for a good mounting "time, temperature, pressure and humidity" did not pull together. In order for your mounting services to be cost and time effective, the four parts of the mounting puzzle should regularly come together into a quality project, one completed with confidence, predictability and END
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Additional information on mounting basics is found in
The Mounting and Laminating Handbook, Second Edition, 2002, and
The Mounting And Laminating Handbook, Third Edition, 2008.
Creative Mounting, Wrapping, And Laminating, 2000
will teach you everything you need to know about getting the most from your dry mount equipment
and materials as an innovative frame designer. All books are available from Designs Ink Publishing through this website.
Chris A Paschke, CPF GCF
Designs Ink Publishing
785 Tucker Road, Suite G-183
Tehachapi, CA 93561