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Articles by Chris A. Paschke, CPF GCF

"Time…How Long Is Long Enough"

April 1992

As I mentioned in January's PFM "Adhesive Trends, Part I", there are a number of controllable elements in the process of mounting or gluing artwork, fabrics and photos to their respective substrates. The ratios of time, temperature, pressure and moisture may vary greatly depending upon the media, mounting process, equipment and adhesive being used. The basics of wet, spray and pressure sensitive mountings follow many of the same rules as for successful "dry mounting", but often 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 in preparation to make the bond. Open times vary depending on the product, so be familiar with your product's proper usage.

Application time (the time it actually takes you to apply the adhesive) 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 placed in an undisturbed area under pressure during that initial set-up time.

Dry Mounting Time

The time it takes to dry mount a project will vary depending upon the adhesive, substrate, size, temperature and item being mounted. Now if that isn't enough to confuse you...there's more. As discussed in "Adhesive Trends for 1992" (PFM, January `92) most tissues and films mount between 165-185ºF. The "dwell time" is the time a project remains in the press to adequately heat all inert materials, squeeze out the air, activate the adhesive and create the bond. The total size of the project and thickness of substrate or mounting board has a direct effect on this dwell time.

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 ½ minute of dwell time the project must remain in the press a total of 2½ minutes the second time. The materials all need to heat to the bonding temperature once again and then add the extra time. Second, as a direct result of having to mount the project an additional 2½ minutes you have now not been time and cost effective. Once again I say, "time is money", do not rush projects only to begin again, try to leave it in the press long enough the first time.

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. THINK!

At the proper temperatures the proper time to leave a project in your press is long enough!

Mechanical Presses

To give you a working average time for heat mounting, I need to address mechanical and vacuum presses individually. Dwell times will vary depending upon the overall size and thickness of the substrate selected, with an average mounting time required for a mechanical press being from 1 minute for and 8x10" mounting to 3 minutes for a 20x24" mounting, or simply 1-3 minutes on the average.

When multiple bites are necessary to accommodate an oversized mounting, these times apply to each individual section not the entire piece. So a two bite 24x36" poster will take approximately 6 minutes of actual mounting time plus perhaps a minute to reposition it for the second bite within the press. You must also take into account the time required to predry (that "moisture" issue) items prior to mounting in a mechanical press. Preparation, assembly and actual press time can take another 1-2 minutes. So mounting a 24x36" poster in a mechanical press could take up to 9 minutes.

Heat Vacuum Presses

When using a heat vacuum press, total "cycle time" for an average mounting becomes 3 minutes for all mountings up to 32x40" and 5 minutes for up to 40x60", or simply 3-5 minutes. The total cycle time includes "draw down time" for the press to pull a vacuum plus actual dwell time. Since predrying is not a required step in vacuum mounting, a 16x20" print will mount in a vacuum press in 3 minutes. It will take the same amount of time to mount this same print in a mechanical press which requires 2 minutes of mount time plus 1 minute of predrying for a total of the same 3 minutes. Now consider the 9 minute 24x36" poster mounted in the mechanical press mentioned earlier, it will take a total of only 3 minutes in a vacuum system.

It is easy to see that mounting time, physical space requirements and anticipated mounting sizes all become important factors when choosing the proper press for your needs (I will discuss this issue in a later article). The important point to remember concerning time is to establish a comfortable working time/temperature ratio.

Average safe mounting times, when the temperatures are also properly set, for a mechanical press run from 1-3 minutes and 3-5 minutes for a vacuum press. Now, I suppose I could have simply said that at the beginning, but then again the issue is time and how long is long enough?

Copyright © 1992 Chris A Paschke

For more articles on mounting basics look under the mounting section in Articles by Subject.
Additional information on all types of mounting is found in:
The Mounting and Laminating Handbook, Second Edition, 2002,
The Mounting And Laminating Handbook, Third Edition, 2008 and
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
Designs Ink Publishing
785 Tucker Road, Suite G-183
Tehachapi, CA 93561
P 661-821-2188