picture mounting

Conservation mounting, protection for your artwork

a picture mountA  picture mount is meant to protect and preserve as well as to decorate and enhance the appearance of an artwork, photo or drawing. Unfortunately, a lot of mounting not only fails to meet this basic criteria, but can also increase damage to the artwork.

Ageing of artwork can happen as a result of exposure to UV light, but more often it comes from acidic tapes, papers, mount board and backing board which leads to the characteristic ‘browning’ of artwork paper after a period of time.

A quote from a document titled, “Caring for your prints, drawings and watercolours” from the National Archives explains –

“Any exposure to light harms media and paper, but poor quality mounting and framing damages more works of art on paper than any other agent. Prints, drawings and watercolours can be ruined through contact with unsuitable framing materials, just as they can by amateur restoration and the use of inappropriate techniques in handling, storage and display.”

Brown frame backing tape used extensively on picture mount
Brown frame backing tape had been used extensively on this picture mount. Both the print and mount would age rapidly with this much acid about.
Brown frame backing tape used extensively on picture mount
Brown acidic frame backing tape used quite extensively on picture this picture mount. Little regard had been paid to preservation! This piece had been mounted by a professional framing company and it was done to a giclée print that had cost the artist more than £100 to reproduce!

In my time as a picture framer I am quite frequently presented with old artworks that require attention due to ageing (browning and warping caused by unsuitable tapes). One piece that was recently brought in was actually glued to the backing board which itself had warped and had started to discolour the print’s paper. Most pieces brought in for ‘restoration’ nearly always require a new mount with suitable tape attachment.

All too often I have come across cheap tapes used by whoever had done the previous mount or frame. This ranges from the cheapest of cheap cellotape or masking tape, to the sturdier, but still inappropriate for mount use, frame backing tapes. Many tapes can also become brittle, lose their adhesive and simply fall off. Believe it or not there are still lots of picture framers doing this poor, shoddy work. I suppose the idea is that they can save a bit of money and no-one will notice when the frame is closed, finished and paid for! However, picture framers should really take on the responsibility of preserving the customer’s work using best conservation practices.

Acid attack on artwork from brown tape
Brown acid ageing of the thick paper on this giclée print had happened due to brown frame backing tape being used for mounting purposes. This happened in a relatively short period of time 1-2 years approximately!

Conservation mounting is the process of using materials and techniques which provide protection to framed works of art on paper and preserving them from this ageing process.

So how do you protect against ageing in a picture mount?


The first step is to choose acid neutral papers, mount boards, other boards and tapes to do the job.

Conservation mount board is quite commonly available these days, and will help reduce ageing. Creating an acid free sandwich of a mount/backing board, ie conservation mount on front with a backing board of conservation mount board before the actual backing board, will also help prevent ageing.

Picture mount / frame layers
The layers involved in a standard conservation picture mount / frame.

I have also successfully used acid free foam board as a good, solid, robust mount backing board for larger prints or mounted prints for display purposes.

Alternatively, for a cheaper but still ph-neutral solution, there are some boards now available that combine waterproof surface, brown backing and a layer of white conservation paper on the face.

These boards are 2mm thick and offer affordable conservation. These boards are quite flexible, however, so for more expensive prints and original artwork, mount board or foam board with a hard MDF type backing would be the better option.

Mount board types

  1. Museum level
    For framing any valued original artwork. Cotton museum grade mount board is made from 100% cotton fibre – a traditional paper-making material, proven stable for hundreds of years. It can be un-buffered (neutral pH) or buffered with an alkali deposit which prolongs the stability of the board and provides some extra protection.
  2. Conservation level
    For framing original artworks. Conservation grade mount board made from chemically purified wood pulp and then alkaline buffered. The core and facings must meet certain criteria such as light fastness, pH ranges and quality of lamination adhesives.
  3. Standard level
    Not recommended for conservation framing. Standard mount board  is made from unpurified wood pulp. Unpurified wood pulp will gradually break down and release acidity, thereby damaging the picture. Although many wood pulp boards are now buffered with an alkali and described as ‘acid-free’, this is misleading. Standard mount board will brown over time and it will produce a brown looking core.


Ph neutral tapes are the best choice for mounting to prevent ageing. They can come in self-adhesive paper, gummed paper and gummed cotton rag variety. The choice of which really boils down to how expensive the artwork is, how long you want to preserve it, or whether you or anyone else for that matter may ever want to be able to reverse the use of the tape by removing it at some point without damaging the artwork. Gummed tape can be removed by wetting, whereas self adhesive tapes would require solvent use. Can your expensive artwork handle a drop or two of water to remove the tape? Or could it withstand a solvent? Perhaps not, but these are valid questions to ask when choosing your mounting tape.

Mounting tape types –
Self adhesive ph7-70 conservation mounting tape Ph7-70 self-adhesive conservation tape: Is a high quality white 70gsm kraft paper tape with acid-free pH neutral acrylic adhesive. pH7-70 tape has excellent ageing qualities. High initial grab, which is helpful for art on heavier paper, and for working with textured or uneven paper and board surfaces. It is self-wound, with no liner to remove, making for faster working. It is ideal for hinging low value prints and artwork into mounts. Would require solvent to remove successfully.
Gummed archival tape Gummed Acid Free (Conservation) Archival Tape: Is a white, gummed, acid-free (pH 7 neutral) paper tape. It is coated with an acid-free, water-based acrylic adhesive system, is non-ageing and therefore will not turn yellow. It can be used in most framing projects for attaching artwork. This gummed tape is designed to allow artwork to be released easily from the tape (with water) and is recommended for conservation standard work.
Cotton rag tape Cotton Rag Gummed Archival Tape: For the ultimate ‘museum quality’ conservation, you can use cotton rag tape made from cotton fibres with a 2% calcium carbonate buffer and naturally lignin (a natural substance in wood derived products that contributes to ageing in papers) free with a pH-range of 7-8.
Ph7-70 acid neutral double sided atg tape Ph7-70 acid neutral double sided ATG tape:  A pH neutral double-sided self-adhesive tape – 19mm x 30m. Conservation grade, pH neutral, double-sided tape, acid neutral, using a water-based, acid neutral acrylic adhesive system which will not react with board or papers and can hence be used for conservation purposes. ATG tape gun compatible, although a tape gun is not required to use it. Important for sticking together double mounts where you are keeping the whole mount environment “acid free”. Cheaper acidic tapes can eventually be seen (as a browning) through the front face of a 1.4mm mount board given enough time.


T-hinge picture mount
A T-hinge is commonly used to attach an artwork to a backing mount board before front mount is placed over it.

The attachment of the artwork to the mount board by tape should be done by creating ‘hinged’ attachment points between the artwork and the mount board. Hinges should allow the picture to hang safely and should be applied only to the top edge of the artwork. The amount of tape attaching to the artwork should really be as little as possibly required to hold it in place without being seen.  On thinner paper types, tape hinges can show through as a bump, so they should always avoid being placed behind the visible area of the artwork.

Hinge types can include T-hinges and S-Hinges both of which can be use to attach an artwork to the backing board. T-hinges are more standard and are stuck to one side of the backing mount board as well as the back of the artwork. They form a T-shape, and allow the artwork to hang and hinge at their attachment point. T-hinges can be paralleled up along the top edge of the artwork being mounted. Lightweight prints may only need 2 T-hinges, heavier ones 4-8 T-hinges, depending on how much space there is along the top edge. This way, you can evenly distribute a long, heavy piece of paper along a row of T-hinges.

S-hinges can be useful if you intend to display the artwork without a top (bevelled) mount.  They actually go through holes cut into the backing mount board and attach to the artwork back and the back of the backing mount board. However, the artwork would still require to be kept from touching the glass (which is one of the main roles of the bevelled top mount), so small spacers would be needed in this case to keep the glass floating from the artwork. These can be hidden under the frame rebate.

Common mistakes

A common mistake found with mounted artwork that I see is that the artwork has been surrounded by tape on all 4 sides (usually with one of the cheaper tapes, as I have mentioned before). This will most likely lead to warping or distortion of the paper or artwork with time as it changes with heat and humidity variations as well as age. When something is held down on all four sides, it has no scope for movement (expansion/contraction) in relation to its surrounding mount. To avoid this, mounts should only be attached on the top edge by tape hinges with the other 3 edges left to float/move naturally. The artwork will still be held in place by the mount itself, but will now be able to expand/contract in relation to the surrounding mount.

It is also common practice to attach the tape to the front mount itself, but you may want to consider that the weight of the artwork may be enough to distort the front mount over time (depending on how sturdy its is) so it may be wiser to attach the artwork with tape to the rear mount board instead, which is a more solid intact piece of board. This technique may not be the best option when you need a precision fit of the artwork to the mount, eg if you are trying to show a 6mm white print border edge the whole way around evenly, where any slight offset may look glaringly wrong.

Materials to use/avoid in conservation mounting

Materials to avoid in conservation mounting Materials to use in conservation mounting
Standard cheap mount board Conservation or Museum grade mount board
Cheap every day tapes
– cellotape type tapes
– masking tapes
– parcel tape
– frame backing tapes
– glues
Conservation grade tapes- ph7-70 self adhesive tape
– conservation gummed tape
– cotton rag tape
Mount backing to acidic brown cardboard or MDF Mount backing to conservation grade mount board or a suitable acid free buffer layer

Other conservation issues

Glass : An artwork should never come in contact with the glass. Spacing the artwork away is necessary for air circulation. The mount usually serves this function, however, sometimes with 3D or deep artwork, eg 3D acrylic, oil paints, sculpted  paintings, tapestries and stitched artwork, it may be necessary to add more spacing. This can be done using double or triple mounts, thick mounts, slips, fillets or special spacers. This will also be the case with frames where it is required that the artwork ‘floats’ on  a backing board with no mount, in which case spacers can be used to lift the glass off the artwork. Special plastic or wood spacers can be utilised which hide behind the rebate.

Light : An artwork can deteriorate with excessive UV light. Pictures should always be kept out of direct sunlight, but even non direct daylight will provide enough UV deterioration. Fluorescent lights are also a strong source of UV. To combat UV the fluorescent bulbs can be fitted with UV filters. UV filtering glass can also be used in the picture frame.

Heat: Excessive heat can easily distort paper, board or backing board, and even the frame itself in worst cases. It is therefore very important to not hang conservation artwork over radiators, fireplaces or any other heat sources.

Humidity: Humidity can be another source of distortion in artwork and mount board, as well as a trigger for mould formation. Damp or humid environments should be avoided where possible.

Insect Ingression: It is quite common to see common dust mites and other small insects crawl through small gaps in frames and work their way into the picture mount. Often dying there and looking like a smudged bit of dirt on the picture mount or, worse still, they may start breeding there! To reduce the chances or insect ingression, you can tape seal the mount/glass sandwich around the edges (with a good quality pH-neutral tape). You will also want to make a good backing tape seal, especially in the frame rebate corners. A final sheet of brown dust cover paper may also be stuck down on the frame rear which will add another layer of protection.


Conservation mounting is not just a concept that should be used by museums and fine art establishments, it should be used as an every day practice at every mounting/framing level to prevent your artwork from brown acidic damage that can happen all too quickly with cheaper materials. Be aware of the potential for some unscrupulous framers using cheap material solutions that are about as far from conservation principles as possible. Every framer should have the responsibility to preserve their clients’ artwork as a primary goal – that is every bit as important as the presentation and final appearance of the framed artwork itself.