If a vintage poster is in bad condition, but it is rare and sought after, it could be worth to restore it. In case of noticeable yellowing or discoloration, bleaching could be necessary. Ask paper conservation professionals to do this, never try it by yourself! They work for museums, archives and collectors, too.
A professional conservation of a vintage poster is an important feature which will increase its value. Main problem is, that vintage posters have been printed on cheap, low quality paper. A backed poster is easy to handle, ready for framing, and it can be rolled for shipping. Please store posters always flat and never rolled!
It took a lot of research to get professional input for this chapter. I would like to say a special "thank you" to:
First: Possibly existing old tapes must be removed by careful use of chemicals. The next step is washing the poster.
Washing allows the fibers to swell open, cleans the surface and neutralizes acidity. In case of being rolled for a long time, the paper can relax now and gets back its original size.
But: If a poster is in very good or mint condition, it is not necessary to wash it before linen backing.
There are many possibilities of paper problems which need professional treatment. Bleaching is only one one of them, please ask restoration studios for help. Be careful, bleaching is definitely NOT HARMLESS! It is a very stressful process to any paper and one that must only be done when all other options are not going to solve the issues.
Be careful: Some kinds of bleaches destroy the bonds between the paper fibers meaning that the paper loses all of its wet strength, it has the consistency of toilet paper when wet. The yellowing process of the paper could be accelerated and worsened. So the effect of bleaching a poster could be that the paper loses all strength and will yellow/brown much more severely after a while.
In case of significant yellowed paper, metal caused dots or foxing (brown dots caused by fungus), it could be necessary to bleach the poster. Bleaching could be done by many different procedures, ask an experienced restoration professional for the best choice to solve your problem. The pictures show partial bleaching at the margins with a brush and in a bath of potassium permanganate.
After a few minutes the procedure is stopped by potassium metabisulfite. Afterwards the poster is washed in water again, a small amount of buffer
(calcium hydroxide) is added to reduce the ph for future. On the one hand this washing to clean away the bleaching agents is very important. On
the other hand it is hard on posters, because the longer you leave a poster in water, the weaker the paper becomes. The binding agents in the paper could break down with water and eventually the
paper falls apart.
is the most common archival poster conservation method, accepted and preferred by dealers, galleries and many collectors worldwide. It provides stability to the poster, it smoothes and flattens
out waves and wrinkles and makes creases and folds invisible or less noticeable. A linen backed poster can be removed by a restorer from the canvas without any damage.
Linen backing usually works like this:
A large piece of artist grade 100% cotton canvas (“linen”) is tacked onto a solid wooden frame ‘stretcher’. It has to be pulled very tight so that there are no ripples and the tension is evenly distributed. Good restorers prefer tightly woven cotton canvas that does not have a strong or noticeable texture which would show through on the finished poster. Next step is mounting a large piece of acid free archival quality paper on the streched canvas. The only glue any linen backer should use, is water based pure wheat starch glue. It is totally reversible and acid free. Best quality is made in Japan, it is highly refined and all natural.
A poster with traces of aging should have been washed, cleaned and (if absolutely necessary) bleached before mounting on the paper backed canvas. The poster has to dry before linen backing. It is
recommended to press the poster against cotton blotter and paraprint/hollytex which absorbs the acidic material and dirt of the washing process.
Mounting the dry (or little moist) poster on the prepared canvas with wheat starch must be done very carefully. It is necessary to remove any remaining creases or bubbles by a really soft bristled brush and a rubber roller. This needs a lot of experience, because there is a risk to damage to the surface of the wet poster or it‘s colours.
The linen backed poster has to dry for some days. In this time it flattens, minor creases and folds disappear. The poster remains on the stretcher until the following restoration process (e.g.
paper replacement, retouches with reversible colors) is completed.
By the way: Air brushing with acrylics or complete over painting on posters is not the way restoration professionals should work. Completely retouched posters looks nice – but it’s value as an original is definitely gone!
Finally the completely dried poster is cut out, leaving a 1 to 1.5 inch margin. This border is left for save handling without touching the poster itself. It also serves to protect the edge of the poster when being shipped or stored. This is the most visible difference to the Japanese paper backing method.
Also called "Japanese Tissue Lining". This is a common archival poster conservation method too. The poster is de-acidified and mounted with wheat paste onto a piece of thin high quality acid free Japanese rice paper.
Paper backing has the same advantages like linen backing, except the stability. But on the other hand it still feels like original paper. In case of framing you don’t need a mat to cover the canvas.
This method is recommended by museums worldwide, a lot of European collectors prefer paper backed posters too.
This poster conservation method is recommended for posters in very good condition only. A starch backed poster has been flattened, cleaned and de-acidified, but fold lines will usually still be noticeable. It’s not mounted to anything, it feels like the original. The backing is made by use of powdered wheat starch and a small amount of buffer (calcium carbonate) mixed with pure water.
Some collectors protect their posters from moisture and dirt by the method of sealing them in plastic film.
It could be a problem for the printing color, if the plastic is not free of solvents or plasticizers. And some types of mold grow better without fresh air.
The best way to destroy a vintage poster and its value, is to use spray adhesive or double-sided adhesive tape. Gluing to cardboard, masonite, wood, aluminum or other rigid materials is unprofessional, too.
NEVER do this!
NEVER buy unprofessionally backed posters!
The last step is restoration of missing or damaged details in the image. Missing areas are replaced by use of original vintage paper similar to the original.
Scratches or missing details in the image are retouched. Professionals will use methyl cellulose to protect the original poster from all colors which are applied for restoring purpose.
A lot of vintage posters have been destroyed by sunlight. Exposure to UV light accelerates the crystallizing of paper’s cellulose chains. It causes premature stiffness, brittleness and discoloration. It will also cause inks, dyes and paints to fade and discolor.
If posters should be displayed, please use proper acid free mats (passepartouts). Framing with 99% UV filtering plexi or protection glass is the only way to protect a poster and preserve its value for many years. Never place framed posters in direct sunlight!
The best thing to do is to change displayed posters twice a year.
I prefer professional frames manufactured by HALBE. These frames are easy to use, a magnetic mechanism allows to change the artwork very comfortable.
HALBE frames are recommended by museums worldwide.
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