Though it is human nature to place blame on almost everything else before we point the finger at ourselves...it is indeed, frequently operator error that triggers most unsuccessful mountings. Last month I said that understanding the elements of time, temperature, pressure and moisture (TTPM) will ensure predictable mounting success. I'm not about to tell you there are no mechanical failures, there are. But they are rare in relation to the stories I've heard about mounting the wrong side of a newspaper clipping, air bubbles as a result of lack of pre-drying, or shall we just turn to "Nightmare On Frame Street".
Predictability should be the hallmark of dry mounting. When repeatedly mounting similar items, the results should be notably similar every time. If your mounted results are less then they ought to be, it can usually be tracked back to one of the key elements.
Wet and Spray Mounting
Temperature is perhaps the only element that most directly relates to heat dry mounting. Most wet and spray glues give directions suggesting recommended storage and preferred room temperatures when mounting. Often they state "for best results...", reinforcing the importance of proper temperatures even with wet glue and sprays.
Freezing winter temperatures restrict shipping of many wet glues and temperatures of below 60F are generally undesirable for most any liquid based adhesive. Excessive cold tends to stiffen and somewhat solidify them or encourage them to clump and/or separate.
Since suggested mounting temperatures for dry mount adhesives and films range everywhere from 150ºF to 225ºF, it is impossible to give the ideal single temperature setting to be used in every situation. The best I can do is try to establish a median or average safe daily temperature that will meet most normal mounting project requirements.
By establishing an average base temperature for as much mounting as possible, idle time waiting for a press to heat up or cool down is minimized. Thus loss of any productive mounting time will be nearly eliminated. Seal Products suggests their mechanical press be set 10 degrees cooler than a hot vacuum press, but I've always set both presses at the same 180ºF. If a number of individuals are regularly using all of the equipment, it removes confusion to maintain the same base temperature on both your mechanical and vacuum presses. Both of my presses remain set at 180ºF for most daily routine projects.
New digital and preprogrammed equipment already carry manufacturer's settings for different types of mounting needs. All you need do is punch in the corresponding program to the mounting you will be doing. The time and temperature will automatically kick in.
Standard Time/Temperature Ratios
When using a mechanical press, set at 180ºF, an 8x10" print requires about 1 minute of mounting time while an 18x24" requires about 3 minutes. It will also take about a minute for the predrying process in both of these instances, increasing the approximate mounting time to 2 minutes and 4 minutes respectively.
In a vacuum press, the same 180ºF will mount either the 8x10" or 18x24" print in about 4 minutes. The physical action of pulling a vacuum will take most of the first minute allowing the remaining 3 minutes for the actual mounting time needed to heat all materials to the required bonding temperature.
"If it takes 4 minutes to mount at 180ºF can't I mount the same item for 2 minutes at 200ºF, allowing me to mount twice as many pieces in the same amount of time?", is a good question. Perhaps in theory this appears correct, but take into consideration having to more closely monitor each project to avoid damage. Now you end up wasting time. Plus, often the one project you could ruin by excessive heat will be the bear you can't replace!
How to Get What you Want
Damage may be defined in many ways. It could simply be a mounting result different from what you might have expected, or what you thought was your desired end product. Individual tissues and pure adhesive films may vary, depending upon the item being mounted, it's thickness or delicacy, it's substrate and the amount of adhesive saturation you wish to achieve.
A 16x20" piece of delicate rice paper with dominant visible silk fibers is to be mounted onto a dark mat board encouraging color tinting for use as a designer mat (see "Color Tinting" September 1994). By using pure adhesive film to guarantee the visibility of the silk fibers by contrasting them against the darker mat board backing, the adhesive's recommended temperature of 180ºF for 2-3 minutes (TTPM) may need to be increased to 200ºF for as long as 15-30 minutes, encouraging saturation.
The longer the rice paper remains under heated pressure (TTPM), at the chosen temperature, the more it will absorb the film adhesive and become more transparent (see "Ghosting Newsprint", November 1991).
Since posters or paper graphics (non-limited editions) often make up a major portion of daily mountings, using rolled tissue adhesive (i.e.: ColorMount, TriMount or TM2) in a press set at 180ºF would be a reasonable selection, a good 80% adhesive. For routine mountings, always extend the time in a press rather than increasing the temperature to accommodate substrate thickness and larger size variations.
Raising Temperatures for Creativity
Multiple 4-ply rag boards with layers of art paper and adhesive between for pin-striped tiered mats may require more aggressive techniques and adhesives. Longer dwell times and higher temperatures often accompany the creation of 8, 12, or 16ply mat boards. Remember the entire mounting package must reach the required temperature in order to begin the bonding process. A denser substrate or multiple layering will always take longer even if the temperature has been increased. These are among the exceptions to standard dry mounting rules.
Wrapping mats and foam in a press is quick, permanent and profitable. All foam boards will compress slightly around the outer edges when placed in any heat press, it's the nature of the beast and will not do damage to the inner mounting. Foam boards will, however, actually begin to melt once they reach an interior temperature of 230ºF. If your press is set at 200ºF and your foam is internally melting (not simply compressing around the outer edges), check your thermostat with indicator strips for temperature accuracy.
Photographs require some care, and extremes of temperature for long durations should be avoided, but you need not be afraid of the mounting process. Watch the time factor! Leave them in long enough to liquefy the adhesive and mount, and be certain to use a breathable tissue (see "Adhesives", July 1994). Horror stories of bubbled photo emulsions at 180ºF are the result of an unusual emulsion problem or non RC photo. This is not a routine sensitivity affiliated with all RC photos.
Photos are frequently laminated, and since manufacturer's suggested press settings for laminating films will vary from 185ºF-225ºF, this clearly illustrates a photograph's tolerance for heat. Ilfochrome Classics (aka Cibachromes) will not physically begin to melt until upwards of 325ºF, though they are best kept out of heat presses altogether for a great many other reasons.
So fear not the lowly 180ºF for mounting photos...just don't leave it in overnight!
Taking your Temperature Seriously
So what temperature do you set your press? A fairly standard, safe setting for daily mountings of paper, photos and fabric will be 180-190ºF in either a mechanical or vacuum press, when using a permanent, breathable tissue. Remember this will vary with different tissues.
More delicate lower temperature formulations will average 160ºF. Always consult suggested temperature settings and remember that lower temperatures will directly reflect the amount of time an item must be left in a press. Lower temps = longer dwell times, and higher temps does not always equal shorter dwell times.
I'll be putting the pressure on next month in part three of TTPM!
Copyright © 1995 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 Publishing
785 Tucker Road, Suite G-183
Tehachapi, CA 93561