CoAC technical drawings in paper impregnated with severe frailty (eng. / Cat.)
Replacement-of-oils-on-impregnated-paper-architectural-drawings
This entry shows the experience of the restoration of several architectural drawings of the College of Architects of Catalonia (COAC) and focuses on replacing those varnishes were impregnated paper. It has been presented in the context of the Symposium Technical Drawings and Their Reproductions under "Replacing lacquers / oils impregnated paper architectural drawings" (The Hague, October 2014).
The vegetables used in paper-so-technical drawings have in common that are transparent, but there are significant differences in their manufacturing process. Therefore both mechanical and chemical and their behavior, properties are also very diverse. The impregnated paper is a type of vegetable paper on which an oil or varnish is applied to make it transparent. The impregnated papers are very fragile and have little mechanical strength due to oxidation caused by the varnish. It is recalled that the oils evaporate through a chemical process (oxidation) and not physical, like water. Varnishes also waterproof, preventing normally cellulose hydrate. When it is shellac, the role inherits the fragility of this rigid varnish.
Drawing impregnated tracing paper, we get fragmented due to its fragility lacerations and broken where there were wrinkles, many times more visible than their own line drawing This fragility may be such that careful handling involves almost inevitable risk of breakage. The loss of flexibility leads straight cuts in the folds (pictured left) and tears in wrinkles (the right). They can be even more visible than the same lines of the drawing. The aims of the restoration are:
Stop oxidation, or even reverse some of its subsequent acidification.
Restore lost flexibility.
Keep strictly the drawing scale (in the case of maps, plans and technical drawings).
Consolidation by adding layers of paper can compromise the transparency that should be maintained as far as possible, thereby restoring lost flexibility is so important, because the more flexible the paper, thinner may be papers we add to reinforce, and transparency will be less disturbed.
The yellowing is not considered a subject in itself, as a rule allows a correct reading of the document (even if the visible effects of acidification does not entail further damage).
TREATMENT:
Remove varnish or oil
This stops further oxidation and decrease somewhat yellowing. The varnish is removed by means of solvents (also depend on the type of oil or varnish). After that the paper becomes opaque, but the aqueous workup was also possible, if desired, since paper is no longer waterproof.
After removing the varnish becomes opaque paper
The same document after removing the varnish is opaque. Note that the fragment of the left (reverse) shows only the part colored by hand, while the right (for the front), teaches only the ink delineated. The loss of transparency means losing the layered effect we had, when we could see lines and colored on both sides simultaneously before.
Impregnated paper restauradoConsolidación
Laminating, if necessary, or simply reinforce the most damaged areas. The adhesive used may be soluble in water or not, depending on the demands of the document (technical, size, damage ...).
Restore lost transparency
It is clear that use the original product is not recommended for the damages involved. But there are still several possible options: Synthetic resins can be used in aqueous or non means. Anyway, these resins returned transparency and also the intensity of tone.
Detail before and after (transparency)
Left: Detail before restoring, with tears where there were creases or wrinkles. Right: Drawing restored with much more flexible role. Note that the paper is substantially more opaque due to the addition of a reinforcement layer over the entire surface, by the reverse. Watercolor had become invisible varnish shows now again becomes visible.
Obviously this also involves waterproof paper again, but this time the varnish will be stable in terms of redox and not cause oxidation, while conferring flexibility to manipulate the security document.
Restoration plan in pencil on tracing paper impregnated (plant Valldemia College.).
Plant Valldemia College. Plano pencil on tracing paper impregnated. Left: before restoring (one of the fragments of the right was preserved even though not in the photo center. After removing the paint, wash and deacidify Right.. After varnishing and laminating Transparency is perceptible in the added lagoons, lighter weight.
Conclusions:
Features Before After Remarks
Transparency harmless ♣♣♣ ♣♣♣ is limited only by adding layers of Reinforced, but not by the varnish.
Tone intensity ♣♣♣ ♣♣♣
Maintenance Scale (technical drawings) must consider in each case acuososo treatments. The scale can be maintained even when strictly aqueous processes involved, but preliminary tests should always be done.
♣♣♣♣ ♣♣♣ yellowing and color depends concetración original varnish, and the degree of oxidation of the paper, which causes the fibers are also more yellow.
Fragility harmful ♣♣♣♣ ♣ Now normal handling is possible without risk of breakage.
♣♣♣♣ ♣ acidity pH increases about 2 points (reaching neutrality) aqueous treatments whenever possible.
♣♣♣ further oxidation - Oxidation is stopped as long as the cause is removed (ie, varnish).