Oddy Test Protocols

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Getty Protocols by Mara Schiro[edit | edit source]

I. Experimental Overview

The principle of the Oddy test is that a sample of proposed storage or display material (the test material) is enclosed in an airtight reaction vessel with three small metal coupons: copper, silver and lead. This is a test of reactivity of gasses that evolve off of the test material, not a contact test so the metal coupons do not touch the test material or each other. The evolution of gases from the material and any corrosion reactions are accelerated by elevating the temperature to 60°C and adding a small amount of water to maintain the relative humidity at 100% for the duration of the test. For every set of samples, one control test is simultaneously carried out with water and the metal coupons but no test material to measure the effects of elevated temperature and relative humidity alone. These coupons in the control environment are called the blanks. After 28 days at elevated temperature and relative humidity, the experimenter visually assesses the degree of corrosion on the test coupons and compares them to the corrosion on the blank coupons. If no alteration has occurred to the test coupons, the material passes. If any corrosion has occurred on any of the coupons, the luminosity of one or more of the coupons has deteriorated or the color of any of the coupons has changed dramatically, the test material fails the Oddy test and the material is not recommended for use. The purpose of this test is not to identify what type of volatile compound is being released from the test material. A failure in the silver coupon could be an indication of the following types of gasses evolving off of the test material: reduced sulfur compounds and carbonyl sulfides. A failure in the copper coupon could be an indication of the following types of gasses evolving off of the test material: chlorides, oxides, and sulfur compounds. A failure in the lead coupon could be an indication of the following types of gasses evolving off of the test material: organic acids, aldehydes, and acidic gases. This list is not comprehensive and should only be used as a starting point for future research if more investigation is required.

II. Materials Coupon size does not effect corrosion but standard sizes are used for consistency of analysis.

1. New or used silver coupons (1 per sample + 1 for control)

1.1. Purity: metal foil of no less than 99.5% purity

1.2. Size: 10 x 15 mm by about 0.1 mm thick Goodfellow Silver foil AG000450/11

2. New or used copper coupons (1 per sample + 1 for control)

2.1. Purity: metal foil of no less than 99.5% purity

2.2. Size: 10 x 15 mm by about 0.1 mm thick Alfa Aesar copper foil 99.9%, 0.254mm thick, Stock #13379

3. New lead coupons (1 per sample + 1 for control)

3.1. Purity: metal foil of no less than 99.5% purity

3.2. Size: 10 x 15 mm by about 0.1 mm thick Alfa Aesar lead foil 99.9%, 0.1mm thick, Stock #42708

4. Felt-tipped rotating polisher Freedom Electric Company, Serial # C850026

5. Metal polish pol metalfledge metal-polish from SPI supplies, Stock #1027

6. Lint-free polishing cloth

7. Mr. Clean liquid cleaning solution

8. Toothbrush or other soft-bristled brush for cleaning

9. Acetone

10. Deionized or distilled water

11. Small well-sealed clean glass jars VWR, I-Chem brand 60 mL jars (P/N 15900-242)

12. Glass ring no more than 3cm in diameter, or beaker of same size (20mL)

13. Glass test tubes VWR, Disposable Culture Tubes (P/N 47729-566)

Durex Borosilicate Glass Size 6x50 mm

14. Clean single-use gloves (2 pairs) VWR, Esteem Stretch Nitrile Gloves (P/N 8817N)

15. Safety glasses

16. Clean tweezers

17. Kimwipes or other lint free laboratory-grade tissue paper

III. Sample Selection

1. The sample should be freshly obtained from the manufacture. • Most materials are most corrosive when first produced and should be tested in this state. • Manufacturers can change formulation of their products at any time without notification so you cannot test an old material if new material will be used.

2. In the case of composite materials (i.e. epoxies) the sample should contain all components in the form that they will be used.

3. Paints, varnishes and adhesives should be tested as freshly cast films.

4. Each sample should be approx. 1x1x1 cm in size to easily fit into reaction vessel.

5. Approximately 2 grams of test materials should be used. With lighter bulkier materials is may be impossible to use that much sample and the following guidelines can be used instead: • Dense materials (i.e. epoxy) at least two 1x1x1 cm cubes • Bulky materials (i.e. foams and boards) four to six 1x1x1 cm cubes • Light materials (i.e. fabrics or paints) ten to twenty 1x1 cm squares

IV. Coupon Preparation

You will need one of each coupon per sample plus one extra of each coupon for the control. For those inexperienced with the Oddy test, consider preparing 2-5 replicates of each sample and of the control to ensure accurate results and prevent false-negatives.

1. Polish Coupons

1.1. Put on clean gloves and safety glasses. 1.2. Cut new lead coupons using clean scissors and set aside until Reaction Vessel Set-Up. • DO NOT polish or wash lead coupons. 1.3. Select new or used silver coupons to polish. 1.4. Select new or used copper coupons to polish. 1.5. Use metal polish and felt-tipped rotating polisher to remove corrosion and tarnish from the front, back and sides of each coupon so that they are untarnished and shiny. • Always wear safety glasses and gloves when polishing. • Polish all silver and copper coupons even if they are new. 1.6. Use lint-free cloth to finish polishing and remove all residue, making sure to thoroughly clean front, back and sides of each coupon. • From this point forward, only handle coupons with tweezers!

2. Clean Coupons

2.1. Put on clean gloves. 2.2. Submerge silver and copper coupons in Mr. Clean liquid cleaning solution. • Mr. Clean is used because (unlike dish soap or detergents) it doesn’t leave a residue. • DO NOT polish or wash lead coupons. 2.3. Remove one coupon at a time from cleaning solution using tweezers and scrub both sides with a toothbrush against the palm of your gloved hand. 2.4. Thoroughly rinse each copper or silver coupon with dionized or distilled water. 2.5. Submerge coupons in acetone. They can either be removed immediately or left submerged for short periods of time while remaining coupons are cleaned. 2.6. Using tweezers, remove coupons from acetone a dry with a kimwipe. 2.7. Using tweezers, carefully inspect all coupons to ensure they are free from tarnish, residue, corrosion, dust or finger prints.

V. Reaction Vessel Set-Up

You will need one reaction vessel per sample plus one extra for the control.

1. Thoroughly clean reaction vessel (I-Chem brand 60mL jar) using Mr. Clean.

2. Rinsing three times with deionized/distilled water and dry with a lint free cloth.

3. Label reaction vessel with a unique sample ID number (instructions below in VII. Using Computer Database VII.22. VII. .2Obtain a new sample ID)

4. With gloved hands, bend each coupons over the glass ring or beaker so that the coupons are suspended in an upside-down U or V shape and don’t touch one another.

5. Gently place ring into jar.

6. Arrange test material samples inside or around outside of ring ensuring that none of the sample is in contact with the coupons.

7. Fill two test tubes with water. If your material is perticuarly absorbent, you may need to fill more than 2 tubes to maintain 100% relative humidity throughout the duration of the test. • The ideal water to air volume ratio of 1:100

8. Check that none of the coupons touch the test material or each other.

9. Tightly seal jars.

10. Place in 60° oven.

11. After a half hour in the oven, re-tighten the jars and return to the oven.

VI. Analysis of Results

1. After 4 weeks (28 days) remove reaction vessels from oven.

2. Open each reaction vessel and using tweezers to remove metal coupons and lay them out onto a labeled piece of paper.

Control Blank Test Material Sample ID Test Material Sample ID Silver (Ag) Copper (Cu) Lead (Pb)

3. Discard test material in trash and discard glass test tubes in glass disposal container.

4. Classify the results for each metal coupon as follows: • P = Permanent. No visible corrosion. Suitable for permanent use. Coupons should not have lost luster on polished surfaces. All copper coupons including the control will naturally turn a darker orange when exposed to heat and humidity. Some lead coupons including the control may acquire a slight purple hue. • T = Temporary. Slight tarnish or film of corrosion, discoloration. In the guidelines for the test these are considered suitable for temporary use. However, the Getty practices a more conservative approach and almost never uses materials that have been deemed suitable for temporary use. • U = Unusable. Corrosion clearly visible. Unsuitable for display case or storage use.

Conservation Materials & Materials Testing