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This month's topic...


Any artwork, whether bought for personal pleasure or for investment, deserves the best type of framing you can afford. A compromise on materials can shorten the life and the value of the image. The following is for the framing of printed works on paper. Oils, pastels, photographs, etc. each have their own specific considerations

The Case for Matting:

The glass used in framing should not come into direct contact with a work of art because:

  1. Condensation can occur, usually due to humidity entering a framed piece through the back, especially if the piece is hung on an outside wall. Condensation is due to a high relative humidity (RH) inside the frame and a cool room temperature outside the frame. Cool air holds less moisture than hot air. 50% RH at 70F is the standard for maximum preservation of framed works. Condensation with time will create a clouded glass on the inside, or even create smoky, fine, sometimes splotchy, mold.
  2. Glass has sodium in it, which can leach out and attract water. The white haze found on the inside of old (and sometimes not so old) glass was tested by a laboratory and found to be Sodium Chloride (NaCl), i.e. the same mineral composition as common table salt.
  3. Surface effects are created when two smooth planes are placed upon each other. "Newton rings", those disturbing halos that are frequently visible on a photograph when the glass is pressed onto to it, can promote ferrotyping, where the surface of the image actually marries to the glass. This can be seen especially in lithographs and serigraphs where the oils will not only fuse to a non-matted surface, they will, over time, actually "jump" the space between a properly installed and matted image to create a grayish shadow or ghost image on the inside of the glass.

You have 3 framing choices on today's market regarding paper mount boards.

  1. Museum or conservation framing in which the papers used are 100% pure rag board with a neutral pH of 7. Rag or Museum boards are fabricated largely of cotton linters, the cotton that is left in the boll after the fibers for other uses have been removed. Because it is not a wood based product, there is no damaging lignin involved;
  2. Cheaper "buffered" (stabilized through addition of neutralizing calcium carbonate) boards that have a life span of about a decade, after which time they should be replaced;
  3. A temporary solution with ordinary (often unlabelled) mat board materials, which is cheap and quick but cheats on protection, and should never be considered for anything "worthwhile".

About paper acids: All wood contains lignin, the resinous brown gooey stuff which breaks down and creates peroxides, acids, and turns brown over time. High Relative Humidity (RH) will catalyze an oxidation reaction. The acids do most of their nasty work in the first 5 years. The peroxides continue to emit for 100 years. Calcium carbonate buffers acid but has no effect on slower acting peroxides.

Obviously your framing decision is tied into the value of the print, but solution (c) should be used only in the case of, say, offset posters.

The window mat was created at the British Museum in the 1850's. Unfortunately that period was also the advent of wood-based as opposed to rag papers. By the 1940's rag boards were once again available, but the "informed choice" was as rare as it was expensive. As a rule of thumb the average mat width is 2-1 /2" to 4". Two inches is the narrowest used at the National Gallery, which does not "weight" the bottom of mats. Adding a half inch or so extra to the bottom cut compensates for the natural slight distortion that the eye creates when "scanning" an image from top to bottom.

In true modern archival framing the whole of the paper is exposed, with the mount just forming a perimeter around the paper. In this way the paper surface is evenly exposed to light, UV or otherwise, and there is less possibility of direct acid transference (that orange-brown line that develops around the cut edges of the mat) if choice (b) is used. Double mats may be attached together with archival quality double stick tape, pure PVA (white) glue or pure starch paste.

The backboard should also be acid-free. Foamcore™ has proven reliable (but long-term usage is still being scientifically monitored). Another choice is Corroplast™, a corrugated plastic that is chemically neutral, but is not advisable in high RH situations, as the corrugations can actually entrap water vapor/condensation. Or: you can effectively and very cheaply cover any quality board with heavy tinfoil (a tip I got from the Tate Modern Gallery, London), which also provides protection from damp and insects, but will exacerbate extremes of temperature in certain environments.

CAUTION: the print itself must never come in contact with the frame or decorative moldings (liners) if these are wood because of wood lignin transfer. If you must use wooden liners (instead of plastic) that rest directly on the image, you can seal the liner with archival framer's tape, or paint the back with basic whitewash paint (the chalky element, calcium carbonate, neutralizes the acidic lignin) or shellac.

How much space is enough, between print and glass? If you touch the glass and it looks like your finger is touching the artwork, it's too close. Ideally all matting should be 4-ply thickness. Avoid simple clip frames as the exposed edges let in moisture, light and dust. Ideally all art should be framed/enclosed with metal frames, but the selection is limited and the results clinical, so aesthetics generally win the day.

When choosing mat board colors, try them out under the type of glass you choose…the gray to green tints in normal glass gradients can vastly alter the whole effect you were aiming for.

The print should be hinged (at the top edge only, to allow for normal expansion and contraction of the paper, depending on humidity) with acid-free pressure-sensitive (peelable), tape to the backing. Over the centuries Japanese tissue has proven the most reliable hinging material. CAUTION: NEVER glue or use double-sided tape or heat-seal the entire print to the backing. If the print is permanently fused to the backing, the picture is considered irrevocably damaged and therefore its value diminishes to near-worthlessness on the marketplace (the exception is in incunabula, where extreme rarity comes into play, and the condition has already probably existed for a few hundred years). We won't even mention lamination (yes, unbelievably that happens, too...)

Glazing and Lighting

Both glass and acrylic let in light so the questions we need to consider are:

  1. Does it have a color?
  2. Does it filter out the most dangerous rays?

Long wavelengths (infra red>700NM) have (low energy, while the more damaging short wavelengths (Ultra violet <400) are high energy. Visible light is in the 400-700 NM band. The damage caused by florescent light can be reduced by the use of UV filtering sleeves. Incandescent light is less damaging. Halogen is midway between florescent and incandescent. The strength (and damaging properties) of light is directly proportional to distance. Closer is worse. Picture lights are definitely a "no" and can cause differential fading. In addition, the heat created by a light so close to the artwork can cause desiccation.

Glass vs. Acrylic - there is no difference in the temperature inside from one or the other. Acrylic is a little better as a thermal insulator, and has its obvious advantage in terms of weight and breakage. However it also attracts dust, and is easily scratched, even in gentle cleaning without the proper fluids. The break resistance of glass is a direct result of the thickness. PPG glass is preferred because it exhibits a gray color rather than the greens of LOF glass. Neither of these can be considered to be an effective UV filter.


True Vue™ conservation glass is not the highest filter product on the market, but is a good product for the price. LAMINATED GLASS by Sandel, a UV filtering and break resistant preservation glass, has the highest UV filtration. Image Perfect™ laminated UV filtering glass, etched to be non-reflective as well as being break resistant, is a new product. All the data is not in, but it seems to be a high quality product. Regular Image Perfect Iminus™ laminate is an affordable, non-reflective glazing with no UV filtering properties.

Laminated Denglass™ has been engineered with a series of coatings so that the reflections are canceled out. It is break resistant and has the highest level of UV filtration (close to 99%). The coatings, however, can give off a bothersome greenish "glow" from certain angles, in the same way that coated prescription glasses can do. Regular Denglass™ has the coatings to cancel the reflections but has no UV filtration.

The main point is to always avoid the cheaper, non-reflective or non-glare types of glass that are etched rather than laminated. Such types of glass so effectively scatter light that they distort the fine lines of etchings or engravings and cut back on color density and intensity. You NEVER find etched anti-reflection/non-glare glass in any quality museum or professional exhibition. The only time it "works" in a non-distortion sense is when this type of glass is in direct contact with the picture. But as soon as you create the recommended gap by using a mount, the picture radically looses its focus, color and clarity.

Final Thoughts

When cleaning the glass of a framed work always spray the cloth first before rubbing. By spraying directly onto the glass it can run down, get caught without your notice between the frame lip and the glass, and seep upwards to moisten or stain the mount or even the picture.

Most importantly, review your framing every few years for signs of mold, foxing, yellowing of the cut mount edges, and the evils of condensation. Keep air circulating between the frame backboard and wall by gluing a small slice of cork to each back corner, especially in high RH climates or for pictures against concrete walls, and especially in newly- built homes that are still drying out. Good quality pure rag art paper is designed to be absorbent for the printing process, but this can backfire on the artwork with incorrect hanging as it just as eagerly absorbs atmospheric moisture and pollutants.

So to summarize the ideal framing job for printed works... mount your art to a neutral backboard using archival tape, mat it carefully with 4-ply archival board, use a good brand of framing glass that offers UV protection, seal the backboard to the frame and hang the frame so that air can circulate between it and the wall. If you light your picture, use a full-spectrum, UV filtered light - keep it out of the sun and away from frame-mounted picture lights.

Responsible state-of-the-art archival care for your artworks is by definition an ongoing process, because

..."A thing of beauty is a joy forever."