resolving the conflict between building preservation and

Res

olvi

ng th

e C

onfli

ct b

etw

een

Bui

ldin

g Pr

eser

vatio

n an

d th

e Pr

oper

Tem

pera

ture

and

Rel

ativ

e H

umid

ity R

equi

rem

ents

of

Col

lect

ions

Mar

ion

F. M

eckl

enbu

rg

Cha

rles

S. T

umos

a

Nov

embe

r 200

3

“Ess

entia

lly, r

elat

ive

hum

idity

expr

esse

s the

m

oist

ure

cont

ent o

f air

as a

pe

rcen

t of w

hat i

t can

ho

ld w

hen

the

air

is sa

tura

ted.

”[a

t a g

iven

tem

pera

ture

]

The

Deh

umid

ifica

tion

Han

dboo

kSe

cond

Edi

tion

Car

goca

ire

Stan

dard

50%

+/-

5% R

H

“The

stan

dard

spec

ifica

tion

of +

/-4

or 5

% in

RH

con

trol

is b

ased

mor

e on

wha

t we

can

reas

onab

ly e

xpec

t the

equ

ipm

ent t

o do

than

on

any

deep

kno

wle

dge

of th

e ef

fect

of s

mal

l var

iatio

ns o

nth

e ex

hibi

t”.

Thom

son,

The

Mus

eum

Env

ironm

ent (

1978

).

Tulip

Pop

lar,

48%

RH

30 S

econ

d In

c. T

est

00.

002

0.00

40.

006

0.00

80.

010.

012

0.01

402468

Stra

in m

m/m

m

Stress (MPa)

Ultim

ate

Stre

ngth

Mod

ulus,

E

Yield

Poin

t

The

Mec

hani

cal a

nd D

imen

sion

al

Res

pons

e of

Cul

tura

l Mat

eria

ls to

M

oist

ure

•ce

llulo

sew

ood,

pap

er•

colla

gen

bone

, ivo

ry, g

lue

•ar

tists

’ pai

nts

pigm

ente

d fil

ms

•m

iner

als

•m

etal

s•

cera

mic

s

Org

anic

Str

uctu

ral C

ompo

unds

Four

bas

ic o

rgan

ic st

ruct

ural

com

poun

dsT

wo

suga

rs: c

hitin

and

cel

lulo

seT

wo

prot

eins

: ker

atin

and

col

lage

n

Cel

lulo

se

New

Sco

tch

Pin

e, T

he T

hree

Prim

ary

Dire

ctio

ns

020

4060

8010

00

0.00

5

0.01

0.01

5

0.02

0.02

5

0.03

0.03

5

Rel

ativ

e H

umid

ity(%

)

Free Swelling Strains

Rad

ial

Tang

entia

l

Long

itudi

nal

R

L

T

Scot

ch P

ine, T

ange

ntial

Dire

ction

020

4060

8010

00

0.00

5

0.01

0.01

5

0.02

0.02

5

0.03

0.03

5

Rela

tive

Hum

idity

(%)

Free Swelling Strains

Mea

sure

men

t as p

er

Woo

d Han

dboo

k (.0

0044

1 / %

RH)

Inter

med

iate

(30%

to 65

% R

H)M

easu

rem

ent (

.0002

67 /

% R

H)

Cha

nges

in d

imen

sion

are

di

ffus

ion

cont

rolle

dan

d ar

e us

ually

ver

y sl

ow

for w

ood

bloc

ks o

r boo

ks

Radia

l

Long

itudin

al

Tang

entia

l

Tens

ile Te

sts

of B

irch

in th

e 3

Dire

ctio

ns

00.

005

0.01

0.01

50.

02020406080100

120

140

Stra

in (m

m/m

m)

Stress (MPa)

Col

lage

nous

Mat

eria

lsgl

ues,

gela

tins,

skin

s, pa

rchm

ents

, le

athe

rs

Gel

atin

s hav

e be

en u

sed

exte

nsiv

ely

for c

entu

ries a

s gl

ues.

The

gela

tin is

from

rend

ered

ani

mal

skin

s and

bo

nes.

A p

artic

ular

ly st

rong

glu

e is

from

stur

geon

swim

bl

adde

rs. G

elat

ins a

re fo

und

in fu

rnitu

re, s

izes

for c

anva

s pa

intin

gs, i

mag

e em

ulsi

ons f

or p

hoto

grap

hic

prin

ts a

nd

film

s. It

is o

ne o

f the

stro

nges

t of t

he c

ultu

ral m

ater

ials

.

Wal

rus

Tusk

, Tan

g./ R

adia

l Dire

ctio

n

020

4060

8010

0-0

.02

-0.0

10

0.01

0.02

0.03

Rela

tive

Hum

idity

(%)

Free Swelling Strains

.000

205

Stra

in/%

RH

It w

ill ta

ke a

20%

RH

cha

nge

to d

evel

op a

mec

hani

cal s

train

of

0.0

04 w

hen

rest

rain

ed. T

his

is th

e sm

alle

st y

ield

poi

nt.

10 Y

ear O

ld H

ide

Glue

(Gel

atin

)

020

4060

8010

0-0

.03

-0.0

2

-0.0

10

0.01

0.02

0.03

Rela

tive

Hum

idity

(%)

Free Swelling Strains

0.01

The

gel

atin

s eve

n w

hen

rest

rain

ed

can

easi

ly b

e cy

cled

from

50%

RH

+/

-15%

RH

with

out d

amag

e.

20th

Cen

tury

Pho

togr

aphi

c M

ater

ials

The

allo

wab

le e

nviro

nmen

t for

20th

cent

ury

phot

ogra

phic

mat

eria

ls. T

his

incl

udes

the

imag

e em

ulsi

on la

yers

, th

e pa

per a

nd p

last

ic su

bstra

tes,

and

the

dyes

and

silv

ers.

A

CD

B 1 2 4 10 30 100

500

010

2030

4050

6070

8090

100

-30

-20

-100102030

Rel

ativ

e H

um

idit

y

Temperature, C

Gel

atin

Abo

veT

g

Art

ists

’ Pai

nts

This

cat

egor

y ca

n in

clud

e oi

l pai

nts,

acry

lic

emul

sion

pai

nts,

alky

d pa

ints

, egg

tem

pera

, an

d ot

hers

. Low

tem

pera

ture

is a

far g

reat

er

prob

lem

than

low

rela

tive

hum

idity

Whi

te L

ead

in C

old

Pres

sed

Lins

eed

Oil

020

4060

8010

0-0

.03

-0.0

2

-0.0

10

0.01

0.02

0.03

Rela

tive

Hum

idity

(%)

Free Swelling Strains

20 Y

ear O

ld Y

ello

w Oc

hre

in L

inse

ed O

il

020

4060

8010

0-0

.03

-0.0

2

-0.0

10

0.01

0.02

0.03

Rela

tive

Hum

idity

(%)

Free Swelling Strains

Even

with

a d

esicc

atio

nfro

m 6

0% R

H to

30%

RH

the

chan

ge is

only

0.0

05

Napl

e's Y

ello

w, E

quil.

Stre

ss S

train

Tes

ts

00.

005

0.01

0.01

50.

020.

025

0.03

012345

Stra

in

Stress (MPa)

48%

RH, 2

3C

5%RH

, -3C

5%RH

, 23C

Relat

ive H

umidi

ty St

ress

es

Ther

mal

Stre

sses

20 Y

ear O

ld Y

ello

w Oc

hre

Alky

d Pa

int

00.

005

0.01

0.01

50.

020.

025

0.03

0.03

505101520

Stra

in

Stress (MPa)

22.5

C, 5

8%RH

22.5

C, 5

%RH

-5C,

5%

RH

Burn

t Sie

nna

Acry

lic E

mul

sion

Pain

t

00.

10.

20.

30.

40.

50.

605101520253035

Stra

in

Stress (MPa)

23.5

C, 5

%RH

11.1

C, 5

%RH

5C, 5

%RH

-6.6

C, 5

%RH

23.5

C, 4

3%RH

Gla

ss T

rans

ition

Tem

pera

ture

•A

cryl

ic p

aint

s +5

C•

Oil

pain

ts-1

0 C

•A

lkyd

pai

nts

-15

C

Pain

ts c

an su

stai

n fa

irly

larg

e sw

ings

in

rela

tive

hum

idity

. T

ests

indi

cate

s tha

t 40%

RH

+/-

15 c

an

be to

lera

ted

easi

ly. L

ow te

mpe

ratu

res

are

a bi

gger

thre

at to

the

stab

ility

of t

he

pain

t film

s.

Com

pute

r M

odel

ing

of C

anva

s Su

ppor

ted

Pain

tings

Mod

els i

nclu

de a

ll la

yers

of t

he

pain

ting,

line

n fa

bric

, glu

e si

ze, o

il gr

ound

and

the

oil d

esig

n la

yers

.

Env

iron

men

tal S

ettin

gs to

Red

uce

Bui

ldin

g M

aint

enan

ce

Mol

d G

row

th

Eff

ects

of h

igh

rela

tive

hum

idity

can

be

loca

lized

; by

lack

of a

ir c

ircu

latio

n an

d/or

by

cond

ensa

tion

Inap

prop

riate

rela

tive

hum

idity

ca

n ca

use

salts

to m

igra

te to

the

surf

ace

of c

eram

ics o

r to

acce

lera

te

reac

tions

at t

he su

rfac

e of

obj

ects

.

Met

al c

orro

sion

from

salt

depo

sits

re

actin

g w

ith a

mbi

ent m

oist

ure

So…

.. W

hat I

s the

Rig

ht V

alue

?

Rec

omm

enda

tions

An

appr

opria

te m

useu

m e

xhib

ition

en

viro

nmen

t wou

ld b

e:W

inte

r; 40

% R

H +

/-5%

RH

Sum

mer

; 55%

RH

+/-

5% R

HTe

mpe

ratu

re; b

asic

vis

itor c

omfo

rt

FY 1

993,

Sm

ithso

nian

Ene

rgy

Cos

ts

HM

SGR

ENAI

&SI

CH

NM

AHQ

&FN

.G. M

SCN

ASM SE

RCN

MAI

AAPG

NM

NH BA

R HPR

I.RES

. SH

01234565.

34.

6

2.89

2.74

2.72

2.57

2.5

2.13

1.97

1.7

1.65

1.46

1.23

0.75

0.85

40.

48

Build

ing

Energy Cost/Sq. Ft ($)

Elec

trici

tyG

as, S

team

, Oil

NG

AN

AS

M

NM

AH

Ren

wic

k

Free

r/Qua

d

SA

AM

/PG

Priv

ate

Res

iden

ceS

ilver

Hill

HS

GM

HS

GM

NM

NH

FY 1

993,

Sm

ithso

niam

Ene

rgy

Cos

ts

05

1015

2025

300123456

Ann

ual R

H, R

ead

50%

RH

+/-

Energy Costs per Square Foot

New

Sm

ithso

nian

Env

iron

men

tal

Gui

delin

es

“For

gen

eral

col

lect

ions

and

pub

lic sp

aces

….

70 +

/-4

degr

ees F

and

Rel

ativ

e H

umid

ity a

t 45

+/-8

%.“

Oct

ober

200

3

Mar

ion

F. M

eckl

enbu

rgm

eckl

enbu

rgm

@sc

mre

.si.e

duC

harl

es S

. Tum

osa

tum

osac

@sc

mre

.si.e

du

(301

) 238

-370

0 x

118

Smith

soni

an C

ente

r for

Mat

eria

ls

Res

earc

h an

d Ed

ucat

ion