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Articles by Chris A. Paschke, CPF GCF

"Substrates—Getting To Know You"

February 1996

Many classes have been taught and articles written about Japanese hinges, mylar corners and the right way to handle artwork when conservation mounting. Yet there still remains a confusion in the framing world surrounding the concept of mounting and its place in relation to the preservation of valuable or collectable artwork at all.

The fact is, utilizing any means of mounting usually covered in this column, whether wet, spray, pressure sensitive or dry, will never fall into the conservation category. Framers are able to select acid-free tissues and tapes, but the fact that adhesive residue will forever remain a part of the original artwork if removed is the point.


Though artwork may not be physically damaged if mounted (a direct result of the inert or neutral nature of an adhesive), once removed from it's backing board or "substrate" it can never again be totally free of adhesive absorption as prior to it's mounting. There will always remain a residue preventing the art to ever returning to its original state. Thus it isn't the adhesive or procedure as much as the altering of the original art itself. So once the decision has been made to go ahead and mount a project we should use the best possible materials available for the chosen job, and that's when knowing your substrates will definitely help.

Following Through

Mounting boards or "substrates" are the base to which a project is affixed to create the foundation for a poster or photograph. Whether Japanese hinging or dry mounting an item, through preservation or simple custom framing, the selection of the right substrate for the job is as important as selection of the right adhesive.

It's terribly important to be consistent with material selection through the entire job. Spray mounting to a 100% cotton rag board might be as mismatched as utilizing all preservation framing procedures then glazing without a UV glass. It's a matter of following through with the chosen concept. If acid-free mats are chosen, then acid-free mounting substrates and neutral pH adhesives should follow. Using an acid-free or inert adhesive on an acidic substrate still equates to potential acid burn. Just as a non-neutral tissue core on an acid-free foam is futile.

Twenty years ago the substrates of choice were either corrugated cardboard, 4-ply paper matboard or varying thicknesses of grey chipboard. Today, if a project has no need for conservation procedures, traditional mount boards have now been joined by regular foam boards, acid-free boards, preadhesived boards, surface colored boards and a variety of plastic based boards.

Substrate Basics

Whether used for mounting or as a filler, rigidity is the main purpose for backing boards or substrates. The Europeans continue to use a great deal of grey chipboard and masonite or their framing, which is much less common in the US. Generally ⅛" thicknesses are recommended for mounting most pictures though thinner boards might be selected for prints less than 8x10". Be aware of the high acidic factor when using regular mount board, chipboard, masonite or plywood as a substrate.

Think about even short term effects of using acidic materials, like newsprint. Even inexpensive posters or newsprint can show accelerated aging and yellowing damage when a non-buffered acidic substrate is used. I have examples of test mountings where the edges have turned significantly yellow within six months of initial mounting.

Using too thin a substrate for too large a mounting will encourage warping of the mounted board. This may be countered by mounting something similar onto the back, but it is better to select a heavier board for larger pieces in the first place.

Foam Boards

The lightness, rigidity and ease of cutting is what foam board has become known for. Foam boards are available as regular clay coated, colored surface paper, acid-free, and 100% cotton rag. Regular boards are available with both white and black core foam, and a variety of both white and black surface papers in an assortment of sizes in ⅛", ³⁄₁₆" and ½" thicknesses. This extensive selection allows for choosing the correct board to fit each framers needs. Foam boards are probably used more than any other board for mounting in the United States as the grey board is in Europe.

Acid-free foam boards are also frequently used as filler or backing board behind hinged museum 4-ply boards in conservation applications. They are noted as the current foam board of choice. Using acid-free foam creates more of a consistency of selected materials in a framing package if all the mats and boards are acid-free or acid-buffered. Specialty niches have been filled by foam manufacturers as new demands have arisen. The 100% cotton rag foam by Bienfang meets surface paper conservation quality sggestions for both backing for hinging or mounting.

Black surfaced foam boards work well for color control when color tinting or control of ghosting is required. It is a great choice for posters with exposed bevel edges to give a more finished look to the mounting. Foams with colored surface papers are good when attempting to control ghosting from lettering on the opposite side. By selecting the mounting surface to match the dominant verso color ghosting is drastcally reduced.

Gatorfoam and the Like

One step tougher than foam and a terrific substrate is Gatorfoam. It is a rigid polystyrene foam with wood fiber veneer applied to either side making it stronger and more durable than other foam products. It is extremely smooth, rigid and resistant to warpage, making it perfect for oversized mountings. One drawback is it's difficulty in cutting. This may be overcome when using certain adaptable wall cutters designed for cutting heavy board such as Masonite and Gatorboard.

Since substrate smoothness is a large issue when dry mounting photographs, this substrate resists denting, scratching and it's smooth surface better prevents "orange-peel", one of the most annoying side-effects to photos. It is available in white, natural and black in thicknesses from ³⁄₁₆" to 1-½" in 4'x8' sheets.

Savage just began advertising a new product "Nucor", sounding much like a product with the rigidity of Gator and the cutting ease of traditional foam. I've not yet tested samples so my information remains incomplete on this one, it looks good.

Preadhesived Boards

Adhesives already applied to foam boards are found as both pressure-sensitives and heat activated types. They are available from a number of manufacturers and only differ from the previously discussed foams in the adhesive is already applied to the surface of the foam board. The substrate structure, rigidity and ease of sizing all remain consistent as with any foam board. These are a bit of a specialty substrate fitting somewhat better in a discussion of adhesives than substrates. If you work with Ilfochrome Classics or if photo orange-peel is a problem, pressure sensitives might be the substrate answer. Heat activated boards are price comparible to a regular foam board plus sheet adhesive and could be the answer for volume poster production mountings.

Mat Boards as Substrates

4-ply mat board and flaw boards have been used as substrates for a long time, though warping of large pieces is a common problem with mat boards. These should probably not be used as a mounting surface if the print is any larger than 16x20".

Other Boards

Very large oversized posters can be a real challenge and when Masonite, Abitibi board, Beaver board, Gatorfoam, plywood, Plexiglas or Sintra might be selected as a substrate. They will generally mount in a heat press, just make the woods are very dry, and extend the time in a press accordingly. As with heavy woods, plastics might need to be professionally sized for you, and the cost of these larger, harder boards will demand a higher mounting price.

Corrugated Backing Boards

Boards used to fill the space between the substrate and the dust cover are "backing" or filler boards. Most commonly used materials are foam and corrugated boards. Note that mounting onto corrugated cardboard can create a series of ridges under the artwork, not the best visual choice and highly acidic. Corrugated materials range from basic brown cardboard to heat resistant plastics of a water repellent nature, with many types in between. There is a blue-grey corrugated acid and lignin-free, buffered board available through University Products well suited as a spacer or for conservation backing.


How do we wrap it all up? Once the substrate has been selected to mount or hinge the project, complete the job by always maintaining a consistent selection of board types throughout. Acid-free front = acid-free backings.

Selecting the right board as a substrate or backing is as important as selecting the correct adhesive and mounting procedure for any specific piece of artwork. Knowing your materials as well as what's available is a very important part of your job. Basic Upson boards, X, 3X, U, and 2U boards will probably be around for a long time and are frequently used substrates. There are situations where sometimes only the old standby will work, plus familiarity and confidence are very important.

Now with the onset of the 1996 trade show season there will always be many opportunities to find new materials to work with and to better understand the ones you may have been using for years. Remember, the best presentation is often controlled by selecting the right substrate for the job.

Will your board of choice be traditional mount board, foam, Masonite, corrugated or plastic? Depends on the job I guess. But I'm certain it will be the right selection as long as you've gotten to know your substrates.

Copyright © 1996 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