DOCUMENTING THE LIGHT SENSITIVITY OF SPANISH LEVANTINE ROCK ART
PAINTINGS
J. M. del Hoyo-Meléndez
a
, J. L. Le ma
b
, E. López-Mon al o
c
, V. Villa e de
d
a
Labo a o y o Analysis and Non-Des uc i e In es iga ion o He i age Objec s, The Na ional Museum in K akow,
ul. Piłsudskiego 14, 31-109 K akow, Poland - [email protected] akow.pl
b
Depa men o Ca og aphic Enginee ing, Geodesy and Pho og amme y, Uni e si a Poli ècnica de Valencia, Camino de Ve a
s/n, Edi icio 7i, 46022 Valencia, Spain - jlle ma@cg .up .es
c
F ench Na ional Cen e o Scien i ic Resea ch, TRACES UMR 5608 – Uni e si é de Toulouse II – Jean Jau ès. 5, Allée
An onio Machado, 31058 Toulouse, F ance - es he mon al @gmail.com
d
Depa amen o P ehis o y and A chaeology, Uni e si a de València, Blasco Ibañez, 28, 46010 Valencia, Spain -
Valen in.V[email p o ec ed]
KEY WORDS: Exposu e, Ligh , Mic o ading spec ome y, Pho osensi i i y, Pigmen s, Spanish Le an ine Rock a
ABSTRACT:
A case s udy o e alua e he use o mic o ading spec ome y (MFS) o he s udy o colo ed sys ems ound in p ehis o ic ock a
pain ings was conduc ed in he Co a Remígia ock-shel e , Cas ellón (Spain). This ock shel e is pa o he ock a si es o he
Medi e anean basin on he Ibe ian Peninsula included in UNESCO’s Wo ld He i age Lis . Some o he pain ings belonging o his
g oup a e exposed o en i onmen al ac o s including na u al dayligh , wind and ain, depending on he ime o he day and he
season o he yea . The e o e, hei p ese a ion is a majo conce n o s akeholde s and esea che s esponsible o p o ec ing and
s udying hese p ehis o ic pain ings. The expe imen al wo k in Co a Remigia ocused on measu ing he e lec ance cu es (400-700
nm) and de e mining he pho os abili y o a ious a eas con aining ed and black pigmen s on he ock a pain ings. The p elimina y
esul s indica e ha MFS is a sui able echnique o s udying he esponse o ligh o ock/pigmen sys ems ound in ock a si es.
The ad an ages and limi a ions o he echnique a e discussed.
1. INTRODUCTION
The p ese a ion o p ehis o ic ock a pain ings is a p io i y o
cul u al he i age p o essionals a ound he wo ld since some o
hese si es a e exposed o en i onmen al elemen s, which can
accele a e hei deg ada ion inc easing he isk o losing such a
aluable piece o in o ma ion o pas socie ies. Clima e changes
a e ha ing and will con inue o ha e an impac on he a es o
deg ada ion o cul u al he i age si es including open-ai shel e s
con aining ock a (B imblecombe e al., 2011). I is known
ha wa ming empe a u es, highe seasonal a iable
p ecipi a ion, and inc eased wind speeds ha e ad e se e ec s on
hese open-ai shel e s. Local ac o s a e also esponsible o
accele a ing he de e io a ion and may include mois u e
condi ions and composi ion and p ope ies o soils (Giesen e
al., 2014). I has been obse ed ha hese impo an si es a e a
s ake due o he ac ion o he a o emen ioned ac o s in
combina ion wi h di ec sola i adia ion. The e o e, i is hoped
ha his esea ch will con ibu e o he de elopmen o a
eliable p o ec ion plan ha akes in o accoun he po en ial
damaging e ec o sunligh ac ing in conjunc ion wi h o he
expec ed local and global en i onmen al h ea s.
Co a Remígia pain ings can be selec ed as a good example
since hey a e loca ed in a complex opened-ai ock si e ha is
ull o shel e s and con ains a la ge a ie y o depic ions. Co a
Remígia is pa o he Spanish Le an ine ock a pain ings o
he Medi e anean basin on he Ibe ian Peninsula decla ed
Wo ld He i age by UNESCO in 1998. The uniqueness o hese
pain ings in he Eu opean p ehis o ic amewo k as well as he
accele a ed deg ada ion o he si e due o i s geog aphical
loca ion jus i ies he selec ion o Co a Remígia as an ideal case
s udy.
Al hough he p ese a ion o ock a pain ings is an impo an
esea ch opic, he e is a p esen need o de eloping and es ing
new me hods ha can be used o assessing he cu en s a e o
he ma e ials and hei po en ial long- e m beha iou as a esul
o exposu e o en i onmen al elemen s. I is gene ally belie ed
ha ock a pigmen s (i.e. haema i e, limoni e, clay mine als,
and cha coal) a e no e y ligh sensi i e. Howe e , some
au ho s ha e demons a ed ha exposu e o sunligh can ha e
ad e se e ec s on hese sys ems due o he mal and
pho ochemical deg ada ion o he his o ic ma e ials (Díez-
He e o e al., 2009). I has been de e mined ha he mal
de e io a ion is mos ly obse ed in he hos ock and is caused
by he non-uni o m dis ibu ion o empe a u e a he co e o he
ma e ial. Hea ing om insola ion esul s in apid empe a u e
a ia ions on he ock su ace ela i e o i s in e io causing
di e en ypes o physical ailu e, including issu ing, peeling,
laking, and c umbling. On he o he hand, pho ochemical
deg ada ion is ypically expe ienced by he ch omopho es
p esen in he pain laye . This is a su ace e ec and he deg ee
o colo change depends on he chemical composi ion o he
pigmen . Mo eo e , he p esence o ligh deg adable mine als
can also p oduce undesi able changes in appea ance when he
his o ic pain s become in con ac wi h oxygen and wa e .
A adi ional accele a ed aging s udy on su oga e samples wi h
simila p ope ies o hose o ock a pain ings conduc ed by
Da id (2008) e ealed ha binde s can in luence he o e all
pho os abili y o a pain
sys em. Se e al ac o s such as he
physico-chemical p ope ies o he pain sys em and i s la e
in e ac ion wi h he ock suppo can esul in ca aly ic,
negligible, o p o ec i e e ec s on he pigmen s. The binde s
used in he a o emen ioned s udy included six ege able
ISPRS Annals o he Pho og amme y, Remo e Sensing and Spa ial In o ma ion Sciences, Volume II-5/W3, 2015
25 h In e na ional CIPA Symposium 2015, 31 Augus – 04 Sep embe 2015, Taipei, Taiwan
subs ances, namely Ja obá esin, Copaiba balsam, Pequi oil,
Babassu oil, pine esin, and gum a abic. In addi ion, ou
animal-based subs ances we e es ed, namely blood, u ine, po k
la d and egg. The subs a e used was a limes one o he
calca eni e ype om Alican e Spain called Ba eig Azul. This is
a po ous ma e ial wi h ine g anulome y. The s udy included
accele a ed pho oaging es s conduc ed on hese su oga e
samples, bu no es s we e ca ied ou on ac ual ock a panels.
Fo all hese easons, a s udy ha ocuses on e alua ing and
documen ing he pho os abili y o ock a colo ed sys ems on
si e was pe o med by unde aking in si u ligh as ness
measu emen s.
The su ace cha ac e is ics (i.e. colo and pho os abili y) o
ock/pigmen sys ems ound in his Spanish Le an ine ock a
si e we e s udied in si u by e lec ance spec oscopy coupled
wi h accele a ed aging. The echnique p oposed o his
in es iga ion is called mic o ading spec ome y (MFS), which
is a me hod o assessing he suscep ibili y o cul u al he i age
objec s o ligh - ading using a high powe ligh sou ce in
combina ion wi h an op ical se up and a VIS-spec ome e . This
me hod allows eal ime moni o ing o spec al changes o a
small a ea (~0.5 mm) o a cul u al he i age objec by exposing i
o ligh . This me hod was de eloped by Whi mo e and co-
wo ke s (1999) and has been ex ensi ely used o s udy he
ligh as ness o cul u al objec s (Fo d, 2009, del Hoyo-
Meléndez and Mecklenbu g, 2010, Tse e al., 2010). A simila
mic o ading s udy using samples om he Mogao G o oes in
China was p e iously conduc ed by D uzik (2010). Howe e ,
he objec i e o ou s udy was o e alua e he pe o mance o
he echnique on si e. The esul s can be conside ed
complemen a y o o he chemical cha ac e iza ion s udies o
pigmen s p e iously conduc ed on ela ed si es (Roldán e al.,
2010) as well as o ea lie in eg al documen a ion wo k using
2D and 3D digi al echniques (Domingo e al., 2013).
This esea ch speci ically deals wi h he es ing o spec al
echniques in he isible ange ield paying pa icula a en ion
o new de elopmen s in op ical echniques ha ha e an impac
on he ins umen s used o moni o he spec um o cul u al
he i age su aces. In his sense, MFS is a ai ly new echnique
ha p o ides no only in o ma ion abou he cu en s a e o he
ma e ial, bu also gi es in o ma ion abou he po en ial changes
ha he ma e ial may expe ience as a esul o uncon olled and
long ligh exposu e. The accele a ed ligh aging componen o
he echnique p o ides an ideal ool o iden i ying and
implemen ing case s udies ha ha e he goal o s udying su ace
cha ac e is ics and hei in e ac ion wi h op ical adia ion.
The applica ion o mic o ade es ing o e alua ing he
pho os abili y o ock a pain ings was e alua ed ecognizing
i s po en ial as a complemen a y ool o cul u al he i age
documen a ion and chemical cha ac e iza ion. This esea ch
cons i u es a easibili y s udy on he use o his echnique o he
s udy o ock a and i con ibu es o he de elopmen o
expe imen al guidelines as well as o he iden i ica ion o
possible sou ces o e o a he ime o conduc ing mic o ading
moni o ing es s in he ield.
2. MATERIALS AND METHODS
2.1 Rock a pain ings
Co a Remígia is one o he mos s anding si es o Vall o a-
Gassulla egion due o he numbe o mo i s, hei s ylis ic
a ie y and he hema ic con en o he scenes. Disco e ed in
1934, he esea ch wo k –g aphic eco ding and analysis–
de eloped ecen ly in his si e has conside ably inc eased he
numbe o documen ed igu es so a . On one hand, he use o
digi al enhancemen so wa e has allowed us o iden i y a g ea
quan i y o unpublished black igu es. On he o he hand,
ene gy dispe si e X- ay luo escence (EDXRF) and Raman
analysis o hese black igu es has e ealed he use o a black
pigmen o ege able o igin, an unknown p ac ice in his a ea so
a , and e y a e in he es o he Spanish Le an ine ock a
e i o y. The iden i ica ion o his pigmen opens he p ospec
o ob ain a i s absolu e da ing o hese pain ings whose
cul u al and ch onological amewo k emains imp ecise
(López-Mon al o e al., 2014).
The mos adequa e shel e , scenes, and ock/pigmen sys ems
we e selec ed aking in o accoun a iables including colo and
pigmen composi ion de i ed om p e ious chemical analysis
(López-Mon al o e al., 2014); posi ion and accessibili y o he
igu es conside ing he limi a ion o he ins umen ; exposu e o
he depic ions o ligh and o he en i onmen al ac o s. A o al
o six poin s we e de e mined: 3 in ed a eas con aining Fe-
based pigmen s and ano he 3 in da k a eas con aining a black
pigmen o ege able o igin, mos likely coming om cha ed
wood. The c i e ion used o selec spo s o analysis was o gi e
p e e ence o a eas con aining ela i ely highe b igh ness and
colo sa u a ion a e isual assessmen s ca ied ou by a eam o
a chaeologis s and scien is s. This e alua ion e ealed ha some
o he ed a eas ha e lowe ch oma (pigmen sa u a ion) mos
likely due o deg ada ion caused by he en i onmen al ac o s
p e iously desc ibed. In addi ion, zones con aining sal
e lo escences we e a oided in o de o concen a e on he
ligh as ness o pigmen s showing no isible in e e ences.
These a eas con aining well-p ese ed igu es a e gene ally
ound in he uppe sec ions o he shel e s since hey a e be e
p o ec ed om en i onmen al elemen s. In any case, he
selec ed igu es a e ep esen a i e o he o al numbe o
depic ions documen ed un il now in Co a Remígia.
In addi ion, he mos a ou able es ing condi ions we e
selec ed aking in o conside a ion ha pa o he pain ings a e
illumina ed by di ec sunligh du ing a ious hou s o he day
and ha he e a e une en ma e ial p ope ies. These include he
use o a ligh sou ce o accele a ed aging ha ing a simila
spec al powe dis ibu ion o ha o na u al dayligh and
modi ying he o iginal ins umen al se up in o de o include
UV adia ion. I is known ha UV con ains mo e damaging
wa eleng hs han isible ligh and he ading a es o ma e ials
can inc ease when his ype o adia ion is included in he
measu emen . Mo eo e , inding a eas o bo h low specula
e lec ion and absence o sal e lo escence was ollowed in
o de o ob ain eliable da a om he pigmen ed zones.
Expe ience om p e ious documen a ion campaigns has
e ealed ha he o al amoun o di ec sunligh ecei ed by he
pain ings may a y om wo o h ee hou s daily depending on
he ime o he yea . These a e mo ning hou s ha can luc ua e
be ween 7:30 and 10:30.
P e ious esea ch ca ied ou in o he ele an Spanish
Le an ine ock a si es (Roldán e al., 2010) has e ealed ha
he e alua ed zones ypically consis o a calca eous ock
subs a e, pain ed laye s con aining bo h o ganic and ino ganic
pigmen s, and a sal e lo escence laye made p ima ily o
calcium sal s such as CaSO
4
and CaCO
3
. These sal s o m when
humidi y comes in con ac wi h he ock suppo , while la e sal
mig a ion o he su ace is a ypically occu ence. The
ISPRS Annals o he Pho og amme y, Remo e Sensing and Spa ial In o ma ion Sciences, Volume II-5/W3, 2015
25 h In e na ional CIPA Symposium 2015, 31 Augus – 04 Sep embe 2015, Taipei, Taiwan
p ecipi a ion o sal s has an ad e se e ec on he in e nal
in eg i y o he ock suppo since i is known ha mechanical
p ocesses such as expansion and con ac ion ake place due o
d as ic changes in empe a u e expe ienced by he hos ock.
The a eas e alua ed we e hose con aining ed and black
pigmen s. This in o ma ion allowed us o selec he op imal
es ing pa ame e s and modi ying he cu en ins umen al se up
since he p ope ies o he ma e ials unde e alua ion we e he
main ac o s a ec ing he eliabili y and he ep oducibili y o
he esul s. A map showing he app oxima e geog aphical
loca ion o ele an Spanish Le an ine ock a si es along wi h
a gene al iew o shel e numbe V in Co a Remigia a e shown
in Figu e 1.
Figu e 1. a) Map showing he app oxima e loca ion o he si e
in Eu ope (yellow do ). Ma oon colo indica es he a ea co e ed
by Spanish Le an ine ock a ; b) gene al iew o shel e
numbe V a Co a Remígia
Figu e 2 shows a gene al iew o he zone whe e he pain ings
a e loca ed om a nea by obse a ion poin . Mo e de ailed
in o ma ion abou he geog aphical loca ion o Co a Remígia
can be ound in (Po ca , B euil & Obe maie , 1935; Sa iá
Boscowich, 1989).
Figu e 2. View o he hill (pa ly co e ed by ees) whe e he
ock shel e wi h he pain ings is loca ed
2.2 Mic o ading spec ome e
The mic o ading de ice used in his s udy was designed and
de eloped by esea che s a he Na ional Museum in K akow
and a he Facul y o Chemis y o he Jagiellonian Uni e si y
(Łojewski e al., 2011) and i is based on he o iginal p o o ype
designed by Whi mo e e al. (1999). This ins umen consis s o
a high-powe ligh sou ce, a 0˚/45˚geome y op ical se up (Fig.
3) and a VIS e lec ance spec ome e . The high powe ligh
sou ce employed is a HPLS 30-04 solid s a e plasma ligh
sou ce (LIFI) om Tho labs (New Je sey, USA). The sys em
uses ibe op ics o p o ide non-con ac measu emen and
de ec ion. The size o he illumina ed spo is abou 0.5 mm,
while he es ima ed in ensi y measu ed a he spo is 7.0 Mlx.
The spec ome e used is an Ocean Op ics (Flo ida, USA) Jaz
minia u e de ice. The i s isible e lec ance spec um was
used as e e ence and subsequen spec a we e collec ed e e y
60 s o a o al es ing ime o 600 s. The in eg a ion ime was
100 milliseconds and 10 spec a we e a e aged. Whi mo e and
co-wo ke s (1999) ha e obse ed ha ins umen al d i is
accoun able o ΔE* alues, which a e less han 0.2 pe hou .
This is conside ed accep able o easonable sensi i e
de e mina ions o colo changes om ading.
The MFS se up is
p esen ed in Figu e 4.
Figu e 3. Measu emen geome y used o mic o ade es ing.
The illumina ion p obe is used o i adia e he ma e ial a a 0
deg ee angle, while he e lec ed ligh is collec ed by he
obse a ion p obe using a 45 deg ee o ien a ion ela i e o he
sample (Diag am adap ed om Whi mo e e al., 1999)
ISPRS Annals o he Pho og amme y, Remo e Sensing and Spa ial In o ma ion Sciences, Volume II-5/W3, 2015
25 h In e na ional CIPA Symposium 2015, 31 Augus – 04 Sep embe 2015, Taipei, Taiwan
Figu e 4. MFS se up used o e alua e he ligh s abili y o
pigmen s in Co a Remígia
2.3. E alua ion o da a
The Commission In e na ionale de l´Eclai age (CIE) illuminan
and s anda d colo ime ic obse e combina ion used was D
65
and 2 deg ee, espec i ely. S anda d illuminan s a e used in
colo ime y o calcula e he is imulus alues o e lec ed colo s
unde speci ied condi ions o illumina ion. D
65
is a s anda d
illuminan in ended o ep esen a e age dayligh illumina ion
condi ions wi h a co ela ed colo empe a u e o abou 6500 K.
In addi ion o s anda d illuminan s, he CIE conduc ed
expe imen s o quan i y he s anda d obse e since he
knowledge abou he exac dis ibu ion o human ods and cone
pho o ecep o s is limi ed. In addi ion, he is imulus alues
depend on he obse e ’s ield o iew, while he e a e la ge
a ia ions be ween eyes. Wi h he goal o educing hese
a iables, he CIE de eloped a colo -mapping unc ion called
he s anda d colo ime ic obse e . This unc ion ep esen s an
a e age human’s ch oma ic esponse wi hin a 2° a c inside he
o ea since p e ious esea ch iden i ied his angle as he one
con aining he la ges concen a ion o colo -sensi i e cones.
Spec ocolo ime ic changes we e e alua ed using he CIELAB
1976 colo space. This is he mos adi ional colo space s ill
employed in many ields including he i age science. The alues
in he CIE, 1976 colo space a e L*, a*, and b* used o
designa e ligh ness-da kness, edness-g eenness, and
yellowness-blueness, espec i ely. CIE L*a*b* alues a e
calcula ed om measu ed is imulus X Y Z alues and he
co esponding Xn Yn Zn alues o he s anda d illuminan and
obse e combina ion used. Re lec ance spec a o each es spo
we e collec ed and colo di e ences we e calcula ed using he
ini ial spec um as he basis o compa ison. The di e ence
be ween wo spec al measu emen s eco ded a imes
1
and
2
(
2
>
1
) is gi en by:
ΔE* = [(L
2
− L
1
)
2
+ (a
2
− a
1
)
2
+ (b
2
− b
1
)
2
]
½
(1)
whe e ΔE* is he change in colo based on he h ee pa ame e s
explained abo e.
The eac ion a es o he su eyed a eas we e compa ed o hose
obse ed o Blue Wool (BW) s anda ds 1-3 unde he same
expe imen al condi ions since hey a e s ill conside ed he only
easonable e e ence ma e ials o e alua ing he ligh as ness o
unknown colo an s (Bacci e al., 2004). The BW ma e ial is ISO
s anda dized o he e alua ion o pho os abili y wi h BW 8
being he mos and BW 1 he leas s able. A ypical ligh
sensi i i y scale used in MFS is BW 1: ex emely high, BW 2
e y high, and BW 3: high. Ma e ials showing highe s abili y
han BW 3 a e conside ed ela i ely s able o ligh when
e alua ed wi h MFS, while hose showing much highe
pe manence emain ou o he sensi i i y ange o his
echnique.
3. RESULTS
The ligh -s abili y assessmen conduc ed in Co a Remígia
ocused on he s udy o ock/pigmen sys ems con aining ed
and black colo an s. Two pho og aphs showing he app oxima e
loca ion o a ed and a black pain ed zone a e shown in Figu e
5. The i egula i ies o he ock suppo can be obse ed.
Some imes he pain ed a ea can ha e a e y i egula suppo
inc easing he di icul y a he ime o se ing up he
measu emen . The une enness o he su aces and he poo
access o he es ing poin s made he ask o se ing up he
measu emen e y di icul . Ge ing access o he pain ed a eas
was no always ideal due o he lack o su aces a ailable o
place he s and suppo ing he measu ing p obes in o de o
ob ain a eliable measu emen . The e o e, a conside able
amoun o ime was spen on jus se ing up he measu emen ,
while he measu emen i sel ook only 10-15 minu es. The ock
subs a e may also p esen a glossy laye ha can in oduce a
specula e lec ion componen p oducing uns able subsequen
spec a i eco ded in eal ime. Hence, i is impo an o
emphasize ha he MFS ins umen is e y sensi i e o
mo emen and glossy su ace e ec s. This was e idenced by he
ex emely la ge luc ua ions in Del a E* alues (no shown)
some imes egis e ed du ing measu emen s.
Figu e 5. Examples o ed (a) and black (b) pain ed zones
e alua ed in Co a Remígia shel e s IV and V
The es ima ed in ensi y a he illumina ed spo was 7.0 Mlx.
The e o e, a 10-minu e exposu e o he ligh p o ided by he
ISPRS Annals o he Pho og amme y, Remo e Sensing and Spa ial In o ma ion Sciences, Volume II-5/W3, 2015
25 h In e na ional CIPA Symposium 2015, 31 Augus – 04 Sep embe 2015, Taipei, Taiwan
mic o ade es e is app oxima ely equi alen o 1.2 Mlx x h. I
one wan s o co ela e he exposu e ob ained using MFS o he
one expe ienced by he pain ings, a ligh moni o ing campaign
o a leas one yea needs o be conduc ed a he si e. In his
way, he o al exposu e ecei ed by he pain ings can be
calcula ed and any possible co ela ion wi h he exposu e
ob ained using MFS can be s udied. A his momen , he au ho s
do no know wha he ac ual exposu e o sunligh is since he e
a e many a iables ha need o be aken in o accoun . Fo
example, he ypical illuminance o di ec sunligh is
app oxima ely 100 000 lx, while ha eco ded on he shade
emains usually below 10 000 lx. The e o e, i is impo an o
de e mine he numbe o hou s o e an en i e yea when he
pain ings a e exposed o di ec and indi ec sunligh .
A summa y o MFS esul s is p esen ed in Figu e 6. The Del a
E* alues p o ide a quan i a i e way o assessing he sensi i i y
o colo ed a eas. An example o a ed a ea e alua ed (indica ed
by he ed line) shows a simila ading cu e o he one ob ained
o BW 3 con i ming ha his sys em has lowe sensi i i y o
ligh i adia ion ela i e o o he less s able ma e ials showing
ex emely high (BW 1) and e y high sensi i i y (BW 2). A e
10 minu es, i can be obse ed ha BW 1 expe ienced a colo
change wi h a inal Del a E* o 5.5 uni s, while BW 2 and BW
3 a e ela i ely mo e s able wi h inal Del a E* alues o 3.0 and
0.5, espec i ely. Figu e 5a shows one o hese ed zones, which
was loca ed in he head o an animal mo i pain ed in shel e IV.
The a ow indica es he app oxima e loca ion o he i adia ed
spo shown as a black do . The esul ob ained o he ed zones
is expec ed since ed pigmen s mos likely a e Fe-based since i
is known ha hese pigmen s p e ail h oughou he Le an ine
ock a zone (López-Mon al o e al., 2014). These sys ems
con aining Fe-based pigmen s gene ally exhibi good
ligh as ness p ope ies. D uzik (2010) conduc ed a MFS s udy
on ock a samples om China and his esul s on Fe-based
pigmen s suppo his s a emen . In con as , a black zone
con aining an o ganic pigmen ga e a simila esponse o he
one obse ed o BW 2; wi h a inal Del a E* o 2.7 (black
discon inuous line). An example o one o he black a eas es ed
is indica ed by he a ow in Figu e 5b. A ed do shows he
app oxima e loca ion o he e alua ed spo on his depic ion o a
human igu e. I is impo an o men ion ha his is only an
es ima ion o he loca ion o he spo since a e he es i is no
possible o isually iden i y colo di e ences aking place in he
es ed a ea, e en unde a mic oscope. I should be poin ed ou
ha i a ma e ial egis e s a Del a E* ≥ 2, hen he colo change
is gene ally no iceable o mos o he people. This means ha
he magni ude o his change is disce nable by he naked eye.
Mahy e al. (1994) epo ed a jus no iceable di e ence as a
Del a E* o 2.3 o highe o he CIELAB (1976) colo space.
Likewise, simila black a eas con aining o ganic pigmen s can
be iden i ied as sys ems wi h e y high sensi i i y o ligh . None
o he e alua ed zones showed a a e compa able o ha o BW
1, which is conside ed an ex emely ligh sensi i e ma e ial.
Al hough li le o no changes we e obse ed a e compa ing he
ini ial and inal e lec ance cu es egis e ed o he ed zones, i
was possible o de ec spec al changes o he black zone es ed
(Figu e 7). The ini ial spec um o he black zone shows a b oad
band in he 400-800 nm egion wi h a maximum nea 550 nm
gi ing a g eenish hue. A educ ion on he in ensi y o he
spec um o e he en i e egion is obse ed as a esul o
exposu e o he ligh spo deli e ed by he mic o ade es e . This
educ ion in e lec ance indica es ha he colo becomes da ke .
The discon inuous line shown in Figu e 7 co esponds o he
inal spec um ob ained a e conduc ing mic o ade es ing o
he black zone. The a ow indica es he di ec ion o he spec al
change. A e compa ing he ini ial and inal spec um, i can be
obse ed ha he Del a E* o app oxima ely 3 uni s (see Figu e
6) egis e ed o he black pain ed zone is due o a educ ion in
he e lec ance h oughou he en i e isible wa eleng h ange.
Figu e 6. Mic o ading cu es ob ained o one spo pain ed in
ed and second one pain ed in black. The ading a es a e
compa ed o he ones egis e ed o BW s anda ds 1-3 unde he
same condi ions.
Figu e 7. Re lec ance cu es o he black spo pain ed wi h
o ganic pigmen eco ded a he beginning (solid line) and a he
end (discon inuous line) o he mic o ading es .
4. DISCUSSION
I is impo an o highligh ha MFS esul s gene ally only o e
physical in o ma ion abou he pho os abili y o a colo an in a
colo an /binde /subs a e sys em. In his sense, no
cha ac e iza ion o he pigmen s was a emp ed since a spec al
lib a y o pigmen s has no been p epa ed ye . Howe e , he
esul s o a p e ious XRF spec ome y s udy conduc ed on a
ele an si e by Roldán e al. (2010) can be somehow co ela ed
wi h he MFS esul s ob ained a Co a Remígia. Fo example,
Fe-based pigmen s a e known o hei high s abili y a e long
exposu es o ligh and his p ope y was con i med by ou MFS
da a. In con as , he a ea pain ed wi h a black pigmen o
ege able o igin showed highe sensi i i y o ligh han
expec ed o his kind o pigmen . I is known ha e en hough
black ege able-de i ed pigmen s a e ex emely pe manen , hey
may become g eye o less b own ollowing p olonged exposu e
o ligh when in con ac wi h wa e o i impe ec ly ca bonized.
Al hough he o igin o his unexpec ed change is unknown, a
possible hypo hesis is he con ac o hese ma e ials wi h wa e ,
which is known o dec easing he ligh s abili y o his
pigmen . The lowe s abili y o his pigmen can also be due o
ISPRS Annals o he Pho og amme y, Remo e Sensing and Spa ial In o ma ion Sciences, Volume II-5/W3, 2015
25 h In e na ional CIPA Symposium 2015, 31 Augus – 04 Sep embe 2015, Taipei, Taiwan

chemical and physical in e ac ions aking place a he
pigmen /subs a e and pigmen /calci e in e laye s.
These da a can p o ide an ini ial s ep owa ds he c ea ion o a
ma e ials pho osensi i i y da abase, which can enhance he
documen a ion o cul u al he i age objec s by adding a ligh -
s abili y componen . These esul s can be o alue when
desc ibing he pain ings and o explaining hei long- e m
beha iou unde cu en and u u e en i onmen al condi ions.
Visual assessmen s we e conduc ed a e each es wi h he aim
o de ec ing changes on he analysed spo s. Howe e , i was no
possible o de ec any change due o he use o high illumina ion
di ec ly on he pain ings. I is impo an o emphasize ha his
equipmen was designed o s udy museum objec s, which a e
ypically s o ed o exhibi ed unde con olled en i onmen al
condi ions. Since his was he i s ime ha his echnology is
applied on he ield, a ligh moni o ing campaign ha akes in o
accoun many a iables (hou s o di ec /indi ec sunligh ,
cloudy/sunny days, e c.) is needed p io o making any u he
co ela ions be ween he na u al and he a i icial exposu es. In
any case, he au ho s belie e ha a chaeologis s a e now mo e
eage o apply his echnique when s udying ock a si es.
I is impo an o emphasize ha he colo changes eco ded
wi h he MFS need o be analysed wi hin hei en i e con ex . I
is impo an o emembe ha his is a e y small spo o ligh
ac ing on he su ace o a much la ge objec . The ins umen
has he capabili y o inducing colo changes a a sub-millime ic
scale wi h he aim o no lea ing a isible ma k behind. Colo
changes ha ing Del a E* alues o wo o highe a e ypically
de ec ed i he wo a eas compa ed a e ai ly la ge (e.g. simila
pain s applied on wo walls).
The de ia ions o accele a ed aging om na u al aging ha e
been ex ensi ely in es iga ed and he au ho s ecognize ha
MFS is only a su ey echnique ha can help o assess i he e
a e any po en ial pho osensi i e ma e ials in ock a sys ems.
The esul s can be complemen a y o da a ob ained om o he
analy ical echniques as well as o in o ma ion a ailable om
clima e moni o ing s a ions. No p edic ions a e possible due o
he non-linea i y be ween he changes expe ienced as pa o a
MFS es and a ia ions obse ed due o na u al aging
p ocesses.
The applica ion o new scien i ic ools such as MFS in highly
aluable p ehis o ic a was used wi h special ca e.
A chaeologis s as well as cul u al he i age documen a ion
specialis s ypically we e conce ned wi h he use o mic o ade
es ing on ac ual ock a pain ings. Howe e , ou p elimina y
esul s can p o ide answe s o some o he ques ions o mula ed
by a chaeologis s and scien is s cu en ly in ol ed in he s udy
o ock a . Now i is con i med ha MFS is an adequa e
applica ion ool o s udy he long- e m beha iou o ligh o
ock/pigmen sys ems. I is e iden ha in e disciplina y
collabo a ion is needed in o de o conduc a comp ehensi e
s udy o ock a pain ings. The e o e, a mul i- echnique
app oach, which includes mic o ade es ing da a can eally
complemen he documen a ion o cul u al he i age objec s by
o e ing a new dimension in e ms o aging p ocesses and
pho os abili y o colo ed sys ems ound in ock a .
5. CONCLUSIONS
This pape p esen s p elimina y esea ch esul s ha con i m he
alue o in e disciplina y mul i ace ed analysis o be e
unde s anding o cul u al he i age si es. The main esul s
ob ained in he p esen s udy can be summa ized as ollows:
1. MFS is a sui able echnique o s udying he esponse
o ligh o ock/pigmen sys ems ound in ock a
si es.
2. The op imal condi ions o analysing he
pho os abili y o pigmen s in ock a pain ings we e
iden i ied. These include he use o ligh o
accele a ed aging wi h a simila spec al powe
dis ibu ion o ha o na u al dayligh , modi ica ion o
he ins umen al se up o include UV adia ion in he
measu emen s, and inding a eas o low specula
e lec ion o minimize he e o in oduced by glossy
su ace e ec s ha can in e e e wi h he
de e mina ion o he sensi i i y o he pigmen .
3. Sys ems con aining Fe-based ed pigmen s exhibi ed
low sensi i i y o he ac ion o ligh showing a
s abili y simila o highe han BW 3.
4. Sys ems con aining black pigmen s o ege able
o igin we e ound o be e y sensi i e showing a
changing a e simila o he one eco ded o BW 2.
This esul may due o he combined e ec o high
humidi y and ligh i adia ion as discussed abo e.
5. Technology app oaches o bo h pa ne s we e
compa ed and op ions o a comp ehensi e
documen a ion o he pain ings ha includes spa ial,
spec al, and ime componen s we e ou lined.
Fu u e esea ch con empla es u he de eloping and using he
mic o ade es ing equipmen on si e. Once he access and he
ins umen ’s s abili y issues a e sol ed and unde s ood, one o
he main a eas o in e es is o conduc a sys ema ic s udy on a
la ge numbe o pain ings ound in se e al a chaeological si es
wi h he aim o compa ing he esul s and c ea ing a da abase o
colo an s abili y. Fo his pu pose, addi ional sys ema ic s udies
a e necessa y using EDXRF and Raman spec oscopies wi h he
aim o p o iding complemen a y in o ma ion abou he
composi ion o he pigmen s.
ACKNOWLEDGEMENTS
This esea ch was possible hanks o he inancial suppo
p o ided by COST Ac ion TD1201, Colou and Space in
Cul u al He i age (COSCH). The au ho s also would like o
hank he Gene ali a Valenciana o p o iding access o he si e
du ing he measu emen campaign. The analysis and g aphic
digi al eco ding o Co a Remígia pain ings a e pa o he
p ojec s PROMETEO/2008-165 and PROMETEO II/2013-016
o he Gene ali a Valenciana Excellence P og amme, as well as
he “NEOSOCWESTMED” p ojec (nº628428) o he Ma ie
Cu ie Ac ions o he 7
h
F amewo k Resea ch P og amme o he
Eu opean Commission. The au ho s acknowledge he esea ch
p ojec HAR2014-59873-R om he Spanish Minis e io de
Economía y Compe i i idad o p o iding inancial unding ha
will help o inc ease he knowledge on his opic.
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ISPRS Annals o he Pho og amme y, Remo e Sensing and Spa ial In o ma ion Sciences, Volume II-5/W3, 2015
25 h In e na ional CIPA Symposium 2015, 31 Augus – 04 Sep embe 2015, Taipei, Taiwan