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The conservation of the Mercator maps |
Background
The National Archives of Scotland (NAS) collects records from various
sources, including gifts from members of the public for the benefit
of the people of Scotland.
One recent such acquisition was three early maps of Scotland by Gerhard
Mercator (1512-1594) of Duisberg. Mercator issued the first part of
his atlas in 1585, and the third part which contained these three
maps was published in 1595 by Rumbold Mercator, Gerhard’s grandson,
who was the first to use the term atlas. These maps were Mercator’s
first ones of Scotland alone, with Scotland in one sheet and Scotland
on a larger scale on two sheets. The maps show a greater improvement
on his map of the British Isles of 1564, with more accurate details
of the interior and a better outline.
|
NAS ref. RHP 141279/1 |
NAS ref. RHP 141279/2 |
NAS ref. RHP 141279/3 |
In 1604 the Mercator plates were sold to Josse
Hondt, an Amsterdam engraver and map dealer, and from 1606 the atlases
were published by the Hondt firm all over Europe. Editions appeared
with text in Latin, French, Dutch, and German, with the maps remaining
unchanged until 1635. The examples here are in French.
Condition
All three maps are in a similar condition. As they have come from
a bound volume Atlantis Pars Altera, they are folded in half, with
the remains of a thin strip of paper adhered to the fold, possibly
a guard which held the sheet into the volume. They are engraved with
the plate mark visible, and have been hand coloured. It is though
that they were coloured for the customer, maybe at a slightly later
date, as other examples that exist show some uncoloured, and colouring
in different areas. Unfortunately some of the pigments are friable,
and therefore there has been some loss of colour. |
Shows text on reverse of RHP 141279/1
|
Remains of paper guard on RHP 141279/1 |
| The paper is cream coloured, handmade, antique
laid with a countermark and watermark visible, which indicates that
these are folio sheets. Looking closely at the sheets there are also
water spots formed during the paper production. Due to previous water/mould
damage the paper surface is soft in places and has small areas of
loss. The paper is discoloured, with staining, particularly some dark
yellow marking. |
Example of weak area and loss on RHP 141279/1 |
Analysis
It was decided to use a non-destructive method of analysis to help
identify the pigments, namely Multi Spectral Imaging, MuSIS® (see
news sheet 1 for
more information on this process). Following examination of the maps
the greens were identified as malachite and verdegris and the reds
as vermillion, but there was still some uncertainty with the pinks,
yellows and brown. Analysis of all three plans shows that they were
likely to be coloured from the same pallet, with contemporary pigments
to the printing.
Results from RHP 141279/2
| Colour in visible light
|
Absorption in infra red |
Appearance in UV |
Appearance in false colour |
Infra red inference |
| Light green |
Absorbs |
Dark blue/purple |
Blue |
Malachite |
| Light pink |
No absorption |
Pink |
Yellow |
[Rose madder] |
| Yellow, island |
No absorption |
Fluorescence, bright yellow |
White |
Indian yellow |
| Yellow, border |
No absorption |
Darker yellow |
Whitish |
Inconclusive |
| Green/blue |
Absorbs |
Dark blue |
Blue |
Verdegris |
| Red |
No absorption
|
Dark red |
Egg yellow |
Vermillion |
| Dark pink |
Absorbs |
Pink |
Dark yellow |
[Rose madder] |
The yellow staining was also examined, but showed no colour change
or absorption, so was not identified.
Treatment
Mechanical cleaning was carried out to remove dirt on the surface
of the paper. Pigments were tested for fugitivity in various mixtures
of water and water/alcohol. The yellow around the islands and the
verdegris green proved to be very fugitive in water. It is possible
to ‘fix’ these pigments in various ways to enable direct
aqueous treatments which will remove staining and discolouration from
the paper, but due to the areas to be covered and the sensitivity
of the colours it was felt to in inappropriate on this occasion. The
maps were gently ‘relaxed’ using Goretex®, which allows
the paper to take in water vapour slowly. Controlled washing was then
carried out on the bench using damp blotting paper with the map face
up. Although this method of washing is not as efficient as submersion
or float techniques, a fair amount of discolouration was removed,
although some staining remains, in particular the unidentified yellow
marks. This technique also enabled the remains of the guards to be
lifted off and retained.
The pH of the paper measured 4, which is lower than is desirable and
has a damaging affect on the paper. Calcium bicarbonate solution was
applied to the reverse of the sheets to raise the pH to 5.5. Care
was taken not to increase it drastically due to potential colour changes
in the pigments.
As areas of the paper were still soft due to previous damp damage,
a size of 0.5% methyl cellulose with a little alcohol added was applied
to the reverse of the prints.
Repairs were made using handmade Japanese papers, selected for their
strength, flexibility and quality, and were adhered using wheat starch
paste. |
 
Example of weak area and loss repaired, NAS ref. RHP 141279/1
|
Repaired and mounted, NAS ref. RHP141279/1
|
Finally the maps were mounted using museum mount board and stored
in a solander box. Full photography has been undertaken on all the
maps, obverse and reverse, for use in the search room. |
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