Preservation Based on a

Risk Management Approach

Jean Tetreault

Preservation Index

A model based on concept of degree of preservation, priority and value of objects

These concepts can be simulated by (simple) equations

Degree of Preservation (DP)

Period of time (in years) over which the object or collection should have no adverse effect (or minimum risk of deterioration) against one specific or many agents of deterioration.

Such as one adverse effect every 10, 50 or 100 years.

For pollutants (constant level) DP = LOAED/C LOAED: lowest obs. adverse effect dose C: concentration of the agent (pollutant)

LOAED = SO2 conc. x Time

= 450 µg/m3 x 11 days x (1 yr/365 days)

= 14 µg/m3 . yr = 5 ppb yr. (ugm-3yr)

Basic fuchsin exposed to SO2

Determination of DP for B. Fuchsin against SO2

DP = LOAED/C

DP = 14 ug/m3 .yr/ 1.0 ugm3 (in room) = 14 yr DP = 14 ug/m3. yr/ 0.1 ugm3 (in room) = 140 yr

Lot of data on LOAED and pollutant’s level in the new CCI book on airborne pollutants

For a Book collection, you may have different DPs against different pollutants

DP of 10 years against Ozone DP of 50 years against SO2 DP of 100 years against particles (soot)

What is the overall DP for the object against all these pollutants? The lowest DP or average DP

or…

Resistance circuit in parallel1/Ro = 1/R1 + 1/R2 + 1/R3 + 1/R4

Book collection with different DPs against different pollutants

1/R = 1/RO3 + 1/RSO2 + 1/RParticle 1/R = 1/10 + 1/50 + 1/100 Overall R = 7.7 years = overall DP

Exclude synergy effect (p.28) After 7.7 yr, no AE will observable but after many

decades of the trend of AE every 7.7 yr could be quantified.

What can you do to improve the overall preservation of the book collection?

First: improve the lowest DP (DP of 10 years against O3, DP of 50 years against SO2 and,

DP of 100 years against particles)

If improve DP of O3 from 10 to 50 yr; DPo = 7.7 to 20 yr

If improve DP of part. from 100 to 150; DPo = 7.7 to 7.8 yr

Priority

O3 SO2 Particles

AE

Improving the preservation

Luckily available control strategies (avoid, block, dilute, etc) tend to have impact on many pollutants at the same time.

Question. Should we start with the cheapest solutions or with most efficient ones?

Priority

AE

If $$$ $

Planning: may want to accumulate your $ to fix the highest rate of damage first

Priority

AE

$$$ $

Cost is still an important factor as long as we know what would be the benefit: Cost/benefit analysis!

How to help for museums for decision: propose control strategies for different degrees of preservation of collection against pollutants

Low DP (= high risk) such as avoid oil based paints in showcases, basic enclosure…

Decreasing of RH, improving airtightness of enclosure, improving control in room (HVAC), proper selection of display and storage products…

High DP such as high efficiency HVAC system or inert gas enclosure…

Rigorous categories from low to high DP. Accept equivalency such as moderate control in

enclosure or moderate control in room.

Users have to be sure that the fulfill requirements of low DP first. Need balance effort on preservation.

This can be done for each agent of deterioration

An opportunity for the determination of the overall DP of collection against the agents of deterioration by following the progressive set of control strategies.

The user selects the scenario of control strategies for each agent from low to high DP that fit the most of their situation, then, the model can assign an estimated DP in year based on their collection.

Extension of the priority

R = DP (in years)

Notion of Value

Preservation Index

Reference to a preservation target (yr)

Indexes are % of actual DP of the collection compared to the DP targeted against all agents (PIo), preservation of collection against one specific agent (PIa), and the overall preservation of the collection against all agents (OPI).

84

91 84

100

Fictive example

Preservation Index Possible interest for 2 year project for the assessment of

preservation of museums for grant funding gov. program.

Simple to use, selection of best fit scenario per agent Relies on a harmonious equation Transparency Accountability (revised by experts) Self education, decision making On line access Link to fund Self building statistic