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THE HISTORY OF IRON PROTECTION. DESCRIPTION OF

MATERIALS AND EVALUATION OF THEIR PROPERTIES

Heikki Hyh

EVTEK Institute of Art and Design

Department of Conservation

Lummetie 2

01300 Vantaa

Finland

Astra!t

Iron "as een noti!ed as eing a ver# vulnerale material sin!e anti$uit#% Corrosion

and ele!tro!"emi!al p"enomena &ere 'no&n in an!ient Eg#pt and (esopotamia%

Eviden!e of t"is is !opper !oated potter# found in Eg#pt) &"i!" indi!ates t"at

pre!ious metal !oating te!"ni$ues &ere in use some 2*00 #ears ago +Aromaa)

1,,*)1-.%

T"e Eg#ptians developed varnis"es) &"i!" &ere !ominations of natural resins

+sandara! or masti!. and oils% T"ese varnis"es &ere applied "ot as prote!tive !oatings

for iron +/radle# /urns) 1,**) 3.% T"e a!tual reasons for !orrosion) alt"oug"

not understood &ere eplained a!!ording to t"e 'no&ledge availale at t"at time% In

an!ient 4ree' p"ilosop"# all sustan!es !onsisted of four elements5 eart") fire) air and

&ater and !orrosion &as eplained as t"e element eart") &"i!" tends to !ome out from

metal%

Ke#&ords

Iron) prote!tion) organi! !oating

History of Iro Prote!tio

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Alt"oug" !orrosion &as not understood some pra!ti!al met"ods &ere in use to prote!t

iron from !orrosion% T"e 6omans 'ne& t"at iron) !opper and lead !orroded and

developed met"ods to prevent it% A!!ording to t"e literature 7lin# t"e elder +238,

A%D%. re!orded some re!ipes% 9e suggested a miture of itumen) pit!") &"ite lead

and plaster for iron prote!tion and a miture of turpentine and pit!" for ron:es

+ Aromaa) 1,,*)1-.% A!!ording to /radle# and /urns) "is re!ipe for iron prote!tion is

as follo&s5 ;If #ou desire to prote!t iron from rust) give it a varnis" of !eruse) plaster

and tar; +/radle# /urns) 1,**) 3.%

s &eapons and t"e follo&ing

re!ipe for armor &as given # a 4erman aut"or in 1-1-5; 7our olive oil in a "eav#

mortar) stir it &ell &it" a pestle until it &arms itself) put &"ite lead to it and ru it

again until it e!omes la!'% 7our a little oil of tartar in it and &it" ?eat>s foot oil or

old fat ma'e a salve% =mear t"e armor &it" t"e salve; +/radle# /urns) 1,**) 3.%

T"is &as t"e level of prevention of !orrosion in Europe for nearl# 100 #ears%

In !ontrast to t"is) la!$uering as a form of metal prote!tion &as in use "undreds of

#ears efore t"e C"ristian era in t"e Far East% T"e inding medium &as mainl# 6"us

verni!ifera) &"i!" "ardens to an insolule film%

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England t"e lo&er "ull of fast sailing oats &as !overed &it" !opper plates and after a

ver# s"ort period of time t"e iron mounting of t"e rudder !orroded +Aromaa) 1,,*)

1.%

T"e s!ien!e of ele!tro!"emistr# developed during t"e 20t" !entur# and !reated a asis

for t"e effe!tive prevention of !orrosion%

IRON CONSERVATION IN MUSEUMS&

History

Ar!"aeologi!al e!avations in =!andinavia egun on a larger s!ale in t"e eginning of

t"e 1,t" !entur#) alt"oug" smaller s!ale e!avations "ad alread# produ!ed a !olle!tion

of o@e!ts%

At t"is time t"e !onservation of ar!"aeologi!al material &as !arried out # sele!ted

!raftsmen &"o &ere familiar &it" t"e materials +4ilerg) 1,) 10- Ba'osen) 1,)

*1.%

Conservation re!ords in =!andinavia date a!' to t"e end of t"e 1,t" !entur#% T"e

treatments predating t"is period !an e found from letters and ot"er unpulis"ed

sour!es onl#%

In general it !an e said t"at treatment met"ods &ere largel# empiri!al and not

ne!essaril# ased on s!ientifi! prin!iples +4ilerg 1,) 10-.%

In t"e !onservation of anti$uities t"e greatest advan!es &ere a!"ieved at t"e end of

t"e1,t" !entur#% Friedri!" 6at"gen e!ame t"e first dire!tor of t"e !"emi!al

laorator# of t"e 6o#al (useums in /erlin &"en it &as founded in 1% 9is

laorator# &as t"e first museum resear!" laorator# in t"e &orld +4ilerg) 1,) 10-

Ba'osen) 1,) **.% 6at"gen &as t"e first one &"o reali:ed t"at treatment met"ods

s"ould e developed spe!ifi!all# in t"e field of !onservation for progress to ta'e

pla!e%

CONSERVATION TREATMENTS&

Histori!'# o"er"ie(

6at"gen des!ries old met"ods ased on impregnation% T"e o@e!ts &ere treated &it"

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materials su!" as s"ella!) linseed oil) !opal varnis") Vaseline) &aes) fats and ruer %

T"ese treatments &ere supposed to ind loose pie!es and to prote!t t"e o@e!ts from

moisture and ot"er "armful !omponents in t"e air%

6at"gen also states t"at t"ese !oatings on t"eir o&n are effe!tive if t"e !orrosion la#er

is free from !"lorides +6at"gen) 1,) -8.%

A!!ording to 6at"gen t"e est prote!tion against moisture in t"e atmosp"ere is pure

melted paraffin) &"i!" does not !ontain stearin +6at"gen) 1,) .%

In =!andinavia eamples !an e found in ?or&a# and Denmar'% In 130 t"e !urator

of t"e /ergen (useum in ?or&a#) il"elm C"ristie) treated all iron o@e!ts in t"e

museum &it" linseed oil +9ansen 1,,) 1--.%

In 10

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T"ese treatments &ere insuffi!ient % After a ver# s"ort period it &as ovious t"at iron

&as unstale and man# o@e!ts "ad to e retreated) ut t"ere &ere also e!eptions%

OR+ANIC COATIN+ MATERIALS&

Itro*)!tio

After treatment a prote!tive !oating is normall# applied to iron% =u!" !oatings are

supposed to e!lude moisture and s"ould prevent or retard furt"er !orrosion + Keene)

1,) 1.%

T"e performan!e of organi! !oatings is determined # t"e p"#si!al stru!ture of t"e

!oating and "o& it alters upon aging%

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are in!luded in t"e !omposition%

Lipid is a mu!" roader term t"at ma# e used to in!lude all of t"e et"er8solule)

&ater8 insolule sustan!es otainale from plant and animal sour!es% Fats form a

ma@or sugroup of lipids +(ills "ite) 1,) 2- (ass!"elein H Kleiner) 1,) *0

9orie) 1,) 1*0.%

Dr#ing oils "ave een used for impregnation% T"e most !ommon of t"ese "as een

linseed oil ut ot"er oils "ave also een used) for eample normal !lo!' oil%

Even in anti$uit# it &as 'no&n t"at dissolving a resinous material in t"e oil !ould

"arden an oil film% =o8!alled !opal varnis"es or la!$uers !ontained fossil resins su!"

as Congo gum or Kauri% 6e!ent resins in use "ave een s"ella! and dammar%

In general resins !an !over details and e!ome rittle +/radle# /urns) 1,**) 3,38

00 9orie) 1,) Keene) 1,) 2.%

T"e most !ommon dr#ing oil is linseed oil t"at "as een &idel# used for iron

prote!tion and !onsolidation% It is etra!ted from t"e seeds of Limu usitatissimum%

Linseed oil !onsists of mied gl#!erides of saturated and unsaturated fatt# a!ids% T"e

dr#ing !omponents are linolei! and linoleni! a!ids% To a!!elerate t"e dr#ing rea!tion

of linseed oil it !an e "eated to 1*081-0GC &it" t"e addition of !oalt8) manganese8

or lead salts% T"is treatment a!!elerates t"e oidation and pol#meri:ation pro!ess

!ausing t"e oil to dr# faster &it" a lo&er vis!osit# +/radle# /urns) 1,**) 3,

(ass!"elein H Kleiner) 1,) *-8*.%

aes do not form a !"emi!all# "omogenous group% T"e !omponent parts ma# e

"#dro!arons) fatt# al!o"ols) fatt# a!ids) esters of fatt# al!o"ols) esters of gl#!erine or

et"ers and t"eir de!omposition produ!ts% It !an e said t"at a ;true; &a is an ester of

a "ig"er monoasi! fatt# a!id &it" a "ig"er mono"#dri! fatt# al!o"ol%

?atural &aes ma# e of animal) vegetale) mineral or animal origin +Colliers) 1,)

3- (ills "ite) 1,) 18* (ass!"elein8Kleiner) 1,) -08-- 9orie) 1,)

*8,.%

a is not an effi!ient &ater vapor arrier ut it remains sti!'# and in t"eor# !an

spread itself to form an even !oating after damage +/radle# /urns) 1,**) 3,3800

9orie) 1,) Keene) 1,) 2.%

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dissolves in !"lorinated "#dro!arons and "eated al!o"ols% Its melting point is 3 8 2

GC +(ass!"elein8Kleiner) 1,) - 8- 9orie) 1,) 1*3 (ills "ite) 1,) 3.%

T"e most !ommon mineral &a is paraffin% 7etroleum in a !rude form is a !omple

miture of t"ousands of !ompounds) most of &"i!" are "#dro!arons li'e paraffins)

olefins) nap"t"enes and aromati!s% 7araffin &a is produ!ed # distillation from

petroleum% 6efined paraffin &a is a translu!ent) perfe!tl# &"ite material% 7araffin

&aes form large !r#stals &"en solid &"i!" eplains t"eir rittleness% T"e softening

point of paraffin &a is 08-*G!% 7araffin &a &ill dissolve in ordinar# fat solvents

&"en &arm% +Colliers) 1,) 3- (ills "ite) 1,) * (ass!"elein8Kleiner)

1,) -18-2 9orie) 1,) 1,.%

Co!#)sios

It &ill e $uite diffi!ult to @udge t"e effe!tiveness of t"ese organi! !oatings% T"ere are

man# fa!tors) &"i!" "ave to e ta'en into !onsideration5 as t"e o@e!t !leaned

efore !oating and to &"at degree J "ere t"ere an# solule salts remaining after t"e

!leaningJ as t"e !ontinuit# of t"e !oating film !ompleteJ "at is t"e "istor# of t"e

o@e!t after t"e first treatmentJ

A!!ording to Keene it is unli'el# t"at t"e !onsolidants and la!$uers used for

ar!"aeologi!al iron &ould "ave mu!" effe!t on t"e stailit# of t"e o@e!ts%

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Last Centur#% In5 6e!ent Advan!es in t"e Conservation and Anal#sis of Artifa!ts%

7reprints of t"e Builee !onservation !onferen!e 7apers% London5 =ummer s!"ool

press%

Colliers En!#!lopedia% Volume 23% ?e& Nor'5 (a!millan Edu!ational Compan#%

4ilerg) (%) 1,% Friedri!" 6at"gen5 T"e fat"er of modern ar!"aeologi!al

!onservation% AIC Bournal vol 2-% ?o% 2% 1,% T"e Ameri!an Institute for

Conservation of 9istori! and Artisti! or's%

9ansen)B%) 1,,% Konservering av Bernoldsa'er !a% 130810% ?ors'

'onserverings"istorie% In5 7reprints of Konserverinsmidler Konserveringsmetoder%

?ordis' 'onservatorforund OIV% Kongress%

9orie) C)% 1,% (aterials for !onservation%Corn&all5 /utter&ort" Co% Ltd%

Ba'oson) T%) 1,% Iron !onservation at t"e ?ational (useum of Copen"agen 8 past

and present% In5 7reprints of t"e International Counsil of (useums Committee for

Conservation% t" Triennial (eeting Copen"agen 1,% London5 Bames Bames%

Ba'oson) T%) 1,% Iron Corrosion T"eories and t"e Conservation of Ar!"aeologi!al

Iron o

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6at"gen) F%) 1,% Die Konservirung von Altert"umsfunden% 9andu!"er der

Knigli!"en (useen :u /erlin% /erlin5 % =pemann%

6at"gen)F%) 1,2% Die Konservierung von Altertumsfunden% 9andu!"er der

=taatli!"en (useen :u /erlin% /erlin und Leip:ig 5 alter de 4ru#ter Co%

6osenerg) 4%A%) 1,1% Anti$uitPs en Fer et en /ron:e% Leur Transformation et Leur

Conservation% Copen"ague5 4#ldendals'e og"andels sortiment%

=ease) C%) 1,,-% A ="ort 9istor# of Ar!"aeologi!al Conservation% In5 Ar!"aeologi!al

Conservation and Its Conse$uen!es% 7reprints of t"e Contriutions to t"e Copen"agen

Congress 1,,-% London5 T"e International Institute for Conservation%