Oddy Testing Program Operation

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Wiki Contributors: Julia Sybalsky, Devon Lee, Elizabeth Holford, David Thickett, Eric Breitung, Sarah Freshnock, Laura Gaylord Resch, Rachel Heyse, Elena Torok, and Catherine H. Stephens.

4/16/2024 - THIS PAGE IS CURRENTLY UNDER CONSTRUCTION! PLEASE BE PATIENT WHILE WE WRITE THIS. THANK YOU.

Running a Program: Resources, Practical Tips, and Troubleshooting

On this page you will find a selection of resources, practical tips, and troubleshooting suggestions to support Oddy testing. The guidance here is intended to help in staying organized, streamlining, and facilitating greater consistency in test implementation. It includes recommendations for documentation and preparation of samples; a basic kit of tools; more efficient coupon preparation, interpretation, and washing procedures; standardized vocabularies to describe test results; a template for recording results and publishing them to the Test Result Table; and coupon photography workflows. This content is organized to follow the order of operations in the testing protocol; universal guidance is presented first, followed by a few tips that are specific to specific test protocols.

Sample Documentation Guidelines

If test records do not include clear and complete documentation of the materials that were evaluated, it is difficult to apply them in future decision-making, or share them with others. For each material tested, keep records as complete as possible by obtaining a full product name and number, along with an SDS or TDS, prior to starting the test. Additionally, a small swatch or sample of the material can be retained and filed in a sample reference book or bulk box. Both SDS/TDS and material samples should be labeled with the test ID to allow them to be readily associated with test results.

Material Sample Preparation

The following suggestions for preparing samples for Oddy Testing are compiled from guides developed by the Metropolitan Museum of Art (MMA) and the British Museum (BM), with minor adjustments and additions by other contributors.

Material	Suggested Preparation Method
Boards - includes composites (eg. Corian®, drywall), natural ((eg. wood, cotton), and plastic/polymeric/synthetic	Cut with a universal blade band saw into 0.5” cubes. Use a utility knife to produce smaller pieces to make 2.0g.
Carpets - natural or synthetic	Cut with clean scissors or utility knife into 1 x 1” squares. To reach 2.0g, cut pieces that represent the sample’s composition—example: the correct ratio of carpet material, blended fibers in carpet, and base of carpet.
Coated samples (e.g. sealed boards)	Cut the bulk sample to size (2.0g) with a universal blade band saw or clean scissors, as appropriate. Avoid cutting the sample up into smaller pieces. Coat the sample as you would for use. It is recommended to test the coated sample alongside the bulk material and the coating separately to facilitate the interpretation of results. The length of time that the coating is allowed to cure/dry may affect test results, so additional time (4-6 weeks) beyond the manufacturer’s instructions may be considered, if this reflects the manner in which the coating will be used.
Coating - floor (e.g. stain, anti-wear, anti-slip)	Follow manufacturer’s instructions regarding dilution; if to be used dry, paint out on Mylar® or Melinex®, and cure per manufacturer’s guidelines; the length of time that the coating is allowed to cure may affect test results, so additional time (4-6 weeks) beyond the manufacturer’s instructions may be considered, if this reflects the manner in which the coating will be used.
Coating - grease, oil, wax	Into a 5mL beaker, weigh 2.0g of sample. Carefully place into the sample jar. Other borosilicate vessels that fit are acceptable as long as they are no more than 4cm tall.
Coating - paint & primer	Paint material onto a Mylar® or Melinex® sheet and spread to a uniform thickness that reflects how it will be used. Cure the material according to manufacturer’s instructions. The length of time that the coating is allowed to cure may affect test results, so additional time (4-6 weeks) beyond the manufacturer’s instructions may be considered, if they reflect the manner in which the coating will be used. After curing, cut the painted Mylar®/Melinex®, into 1.5” wide strips and weigh to 2.0g, taking the weight of the Mylar®/Melinex®, into account by subtracting it from the total sample weight. Put a small piece of Mylar®/Melinex®, at the bottom of the jar/tube if there’s concern about the material sticking to the glass. Roll the sample strips into a coil with the sample material facing inward, and place in the bottom of the jar/tube.
Coating - protective (e.g. anti-UV, -abrasion, -tarnish)	Paint the material onto a Mylar® or Melinex® sheet and spread to a thickness that reflects how it will be used in the museum. Cure the material according to the manufacturer's instructions. The length of time that the coating is allowed to cure may affect test results, so additional time (4-6 weeks) beyond the manufacturer’s instructions may be considered, if this reflects the manner in which the coating will be used. After curing, cut the painted Mylar®/Melinex®, into 1.5” wide strips and weigh to 2.0g, taking the weight of the Mylar®/Melinex®, into account by subtracting it from the total sample weight. Put a small piece of Mylar®/Melinex®, at the bottom of the jar/tube if there’s concern about the material sticking to the glass. Roll the sample strips into a coil with the sample material facing inward, and place in the bottom of the jar/tube.
Coating - powder	Prepare the material according to the manufacturer’s instructions on lab-grade aluminum foil. After curing, cut the coated foil into 1.5” wide strips and weigh to 2.0g, taking the weight of the foil into account by subtracting it from the total sample weight. Roll the sample strips into a coil with the sample material facing inward, and place in the bottom of the jar/tube.
Fabric - batting & padding, book cloth, or exhibtion/woven	Cut material with fabric scissors into 1 x 1” squares. To reach 2.0g, cut small segments from a 1” square. Samples often need to be folded, rolled or cut up to fit into the jar/tube.
Fiber or Thread	Cut the length of sample that weighs 2.0g. Wind it loosely and neatly around two gloved fingers, remove, and place in the bottom of the sample jar/tube.
Graphics - (e.g. ink on substrate, with or without additional layers)	Cut sample to size (2.0g) with a universal blade band saw or clean scissors, as appropriate, to produce a proportionately and structurally representative sample. Avoid cutting the sample up into smaller pieces. It is recommended to test the composite sample alongside separate components tests (substrate, ink, etc.) to facilitate the interpretation of results. If the sample has sufficient thickness and core material would not be exposed during normal use, see suggestions for “Layered Composites”.
Inorganic - (e.g. fillers, salts, rocks)	Keep the sample as is or prepare it as it would be used. For example, if you are testing salts, do not grind them further unless that’s how they are used. Weight 2.0g of sample.
Layered composites - (e.g. mount boards)	Some samples such as storage boxes or mount boards may have a barrier layer on the outside with a less inert core that would not be exposed during normal use. If you put the sample in the jar/tube with the core exposed, the sample is more likely to fail so it is suggested to seal the edges: Cut sample to size (2.0g) with a universal blade band saw or clean scissors, as appropriate. Avoid cutting the sample up into smaller pieces. Seal the edges with a “Permanent” foil tape.
Metal - mechanical fastener	Place whole fastener in jar/tube.
Paper-based (e.g. folder, cardboard, sheet) or filled (fillers such as silica gel, zeolites, alumina)	Cut material with clean scissors into 1 x 1” squares. To reach 2.0g, cut pieces from a 1” square. Samples often need to be folded, rolled or cut up to fit into the jar/tube.
Paste - filler/binder mixture (e.g. plaster, acrylic spackle, non-paint)	Extrude onto a Mylar® or Melinex® sheet. Spread to a thickness that reflects how it will be used. Cure material per manufacturer’s suggestion. The length of time that the paste is allowed to cure may affect test results, so additional time (4-6 weeks) beyond the manufacturer’s instructions may be considered, if this reflects the manner in which the paste will be used. After cured, peel the material from the Mylar®/Melinex®, if possible and weigh to 2.0g. If the material cannot be freed from the Mylar®/Melinex®, remove excess Mylar®/Melinex® and weigh the material to 2.0g, taking the weight of the Mylar®/Melinex® into account by subtracting it from the total sample weight.
Polymer - adhesive - caulk or sealant	Extrude onto a Mylar® or Melinex® sheet. Spread a thickness that reflects how it will be used. Cure per manufacturer’s instructions. The length of time that the adhesive is allowed to cure may affect test results, so additional time (4-6 weeks) beyond the manufacturer’s instructions may be considered, if this reflects the manner in which the adhesive will be used. After curing, peel the material from the Mylar®/Melinex® if possible and weigh to 2.0g. If the material cannot be freed from the Mylar®/ Melinex®, remove excess Mylar®/Melinex® and weigh the material to 2.0g, taking the weight of the Mylar®/Melinex® into account by subtracting it from the total sample weight.
Polymer - adhesive - glues - liquid (e.g. acrylics, wood glues, starches)	Extrude adhesives onto Mylar® or Melinex® sheeting in a thickness that reflects the actual material application thickness. Cure per manufacturer’s instructions. The length of time that the adhesive is allowed to cure may affect test results, so additional time (4-6 weeks) beyond the manufacturer’s instructions may be considered, if this reflects the manner in which the adhesive will be used. Cut the sample into 1 x 1” squares. Weigh the dried material on Mylar®/Melinex®, taking into account the weight of the Mylar®/Melinex® attached to the sample. To reach 2.0g, cut pieces from a 1 x 1” square.
Polymer - adhesive - heat activated (e.g. hot melt, heat set)	Extrude lines or strips of melted material onto aluminum foil. Allow to cool. Peel from aluminum foil and weigh out 2.0g of sample. If material does not remove from foil, repeat on Mylar® or Melinex®, attempt to remove. If not removable, and account for the weight of the Mylar®/Melinex® in weighing the sample.
Polymer - adhesive - pressure-sensitive - single sided	Cut 2” lengths of tape, taping the adhesive sides to the backed sides to form a small 2.0g block of tape. Place the sample onto Mylar® or Melinex® to protect the jar/tube from the adhesive. Roll up the finished sample to fit it in the jar/tube.
Polymer - adhesive tape pressure-sensitive - double sided	Fold the tape onto itself “accordion style” every 2” while removing the backing. Put 2.0g sample on a piece of Mylar®/Melinex® to protect the jar/tube from the adhesive, and carefully place in the bottom of the jar/tube.
Polymer - block/bulk/pellet	If material comes in a block, cut into 0.5” cubes using a band-saw. If the material comes in small pellets that fit in the sample jar/tube, use whole uncut pellets. To reach 2.0g, shave material from one cube or pellet using a utility knife.
Polymer - foam - building insulation or non-insulation	For dense foam, cut with a universal band saw into 0.5” cubes. To reach 2.0 g, remove material from one cube using a utility knife. For soft foams, cut material with clean scissors into a 1.5” wide strip that weighs 2.0g. Compress the strip into a roll, and insert into the bottom of the jar/tube. Make sure the foam does NOT touch the metal coupons when it expands.
Polymer - foam sealant	Cut material with clean scissors into a 1.5” wide strip that weighs 2.0g. Compress the strip into a roll, and insert into the bottom of the jar/tube. Make sure the foam does NOT touch the metal coupons when it expands.
Polymer - gasket	Cut material with clean scissors into 2” length strips.
Polymer - glove	Cut material with clean scissors into 1 x 1” squares. To reach 2.0g, cut pieces from a 1” square. If you want to know the impact of a particular glove on the corrosion properties of the metal (as the result of contact), put on afresh pair of gloves and rub each coupon for 10 seconds, on both sides, using a different section of the gloves.
Polymer - membrane (<1mm thick)	Cut material with clean scissors into 1 x 1” squares. To reach 2.0g, cut pieces from a 1” square. Samples often need to be folded, rolled or cut up to fit into the jar/tube.
Polymer - sheet (>1mm thick)	Cut material with clean scissors into 1 x 1” squares. To reach 2.0g, cut a minimal amount of strips from a 1” square. Samples often need to be folded, rolled or cut up to fit into the jar/tube.

Tools

A basic set of tools and implementation of a few practical tips make preparation of metal coupons faster and easier. A suggested tool kit for cutting, manipulating, and handling coupons during test assembly includes:

• Scissors
• Metal ruler, approximately 6 inches, marked to emphasize measurement increments used in cutting metal coupons
• Awl or needle tool
• Scalpel with #11 blade
• Pointed tweezers
• Blunt tweezers
• Paddle tweezers

By designating one set of tools for each of the three metals, and a fourth set for processing samples, colleagues can work simultaneously to prepare coupons, while also reducing the risk of transferring dissimilar metal shavings and sample residues onto them. To help stay organized, tool sets can be labeled and segregated in separate baskets.

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Coupon Preparation

Watch glasses containing lead, copper, and silver coupons.

Metal foil sheets are sensitive to handling and environmental conditions, and it is not uncommon to receive metal that exhibits manufacturing flaws such as scratches, fingerprints, tarnish, and residues. Metal with manufacturing defects should not be used to prepare Oddy test coupons if at all possible. Ideally, it should be returned to the vendor and replaced with undamaged metal. If this is not possible, coupons may be cut from the unaffected areas of the foil sheet, though this alternative is obviously more costly. If blemished metal must be used, consistency across all coupons in a batch (including controls) should be prioritized; and flaws should be well documented in the test record as a reference during the interpretation of results. Even so, flaws may make rating materials difficult or impossible if change cannot be accurately judged relative to the control. There is greater likelihood of accurately interpreting test results if metal with minor flaws is used only for materials that are expected to test poorly.

A silver foil sheet delivered with hazing and rainbow tarnish along the top half.

A copper foil sheet delivered with irregular reddening and scratches along the surface.

When setting up multiple tests, it is generally most efficient to prepare all coupons of one metal before moving on to the next. Doing so also makes it easier for multiple people to work together, each taking one metal. Coupons can be placed in petri dishes or watch glasses for short-term storage between preparation steps. Contained this way they can be safely moved around the workspace if needed without direct handling that could cause contamination, scratches, etc.

A needle awl is useful for marking metal foil sheets so that they can be cut to size. However, take care not to leave stray score marks or divots in the foil that remain after cutting; these surface irregularities can corrode preferentially in testing, complicating assessment.

Silver foil sheets are available with mirror and striated finishes. Both can be used in Oddy testing, but interpretation is more consistent if one routinely selects one finish or the other. It is not recommended to mingle coupons with the two finish types within the same batch, since distinguishing subtle differences between coupons during assessment is more difficult when comparing striated and mirror-finished silver. For the same reason, when using striated silver, it is preferable to consistently orient the striations parallel to either the long or short side of the coupon.

Special consideration should be given to preparation of the lead coupons, as the lead metal foil is soft and easily scarred, excessive sanding may burnish the surface, and generates hazardous waste. It can be challenging to achieve an even surface quality with sanding and polishing, and it is recommended that this step be completed by the same hand for the most consistent results. The Met’s protocol contains video demonstrations and descriptions of how to consistently prepare lead coupons.

Holding the lead metal foil with a Kimwipe over a gloved finger while sanding can mitigate the risk of scratching or marking the delicate surface. To remove lead particulates, a lab wash bottle can be used to flood the surface with solvent, reducing the need for physical contact with the lead surface. Due to its malleability, lead can easily be cut with either a scalpel or scissors. A self-healing cutting mat may be designated for scalpel cutting.

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  Marking silver foil with a needle tool.

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  Scoring silver foil with a needle tool.

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  Cutting silver foil with scissors.

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  Holding a strip of lead foil with a Kimwipe over gloved hands.

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  Flooding lead foil with acetone from a lab wash bottle.

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  Cutting lead coupons to size with a scalpel over a Kimwipe-lined self-healing cutting mat.

Test Assembly

Once coupons are prepared, each set can be secured to its stopper or coupon hanger. Lead coupons are fragile and easily deformed, and it’s preferable to attach them last. When all tests are assembled, conduct a final review of each jar or tube to ensure that all required components are present, coupons are secure, and they are not touching one another, the jar, or the sample (unless a contact test is preferred).

When loading the oven, consider whether multiple batches are or will be aging simultaneously. The first batch into the oven will be the first out, so it is inconvenient for it to be pushed to the back by subsequent batches. To expedite retrieval, load each batch into the oven from back to front, with separate batches arranged side-by-side. Organized this way, one can quickly locate and remove all the tests in a single batch without rearranging the entire contents of the oven.

Coupon Assessment

Canning weights.

Coupons flattened between two stacked canning weights

When aging is complete and tests have been disassembled for interpretation, any bent metal coupons can be flattened using glass canning weights. These weights are inexpensive, heavy, smooth, and can be easily cleaned of any corrosion products left behind by the coupons. A metal coupon can be placed on one glass weight with tweezers and gently pressed beneath a second one. Avoid twisting the weights while pressed together to prevent scratching the metal coupon.

When completing a larger batch of tests, some simple adjustments to your workflow can help to stay organized during the assessment of results so that data is recorded accurately for each material tested.

Metal coupons from the A and B replicates can be differentiated for assessment and imaging with metal punches. Small dog ears at the upper corners of the Control coupons can also be used to distinguish them from sample coupons and make them easier to move around with tweezers for comparison.

Cafeteria or other trays can be used to contain and move disassembled tests during assessment while keeping coupons associated with their respective Sample IDs and reusable components (important for limiting reuse to components from “Permanent” and/or “Temporary” tests). By lining them with Kimwipes or paper towels, coupons are kept clean while also providing a place to jot down ratings assigned to replicate or test. The interpretation of Oddy test results is inherently subjective, but is made much more consistent through the use of controlled vocabularies. Another way to manage this subjectivity is to conduct coupon assessment as a team, assigning ratings through consensus. Clear roles can help people to work efficiently together. For example, in a team of three, one person might handle the A replicate coupons, while a second handles the B replicate coupons, and a third records observations and results. To facilitate easy movement around the table, A, B, and Control coupons can be placed into separate petri dishes.

A and B replicate Control coupons differentiated with metal punches.

A petri dish containing A replicate Control coupons with dog-eared upper left corners.

Oddy test ratings marked in red on a paper towel lining alongside disassembled tests and coupons.

Standardized Corrosion Vocabularies

Controlled vocabularies help to standardize the description of corrosion phenomena between tests and evaluators. The Metropolitan Museum of Art (MMA) has produced three glossaries of commonly-observed corrosion that are illustrated with current photos of scored coupons. All coupon images in these documents are linked to their original high-resolution photographs stored on the AIC wiki. They can be downloaded using the links below:

• Copper Corrosion Library
• Silver Corrosion Library
• Lead Corrosion Library

All coupon images in these documents are linked to their original high-resolution photographs stored on the AIC wiki.

Template for Recording Results

Assessment of a batch of Oddy test coupons. Julia Sybalsky assesses the A replicate coupons, Gabrielle Tieu assesses the B replicate coupons, and Devon Lee (not shown) records observations and Oddy test ratings.

A spreadsheet template has been developed for recording Oddy test records. The template is compatible with the commonly-used testing protocols, and includes a tab that formats results for easy upload to the Test Results Table. Instructions for uploading are also available.

Washing

Depending upon the washing procedure selected, cleaning the glassware and other components used in Oddy testing may require steps to be completed over several days. If one has multiple loads of glassware moving through those steps, or multiple people helping to keep things moving along, labeling becomes more important for staying organized. Reusable laminated cards are a nice option for keeping track of the status of each tub, beaker, or tray of test components in the washing process, and can be used to record the time/date, initials, washing step, and the type and count of components in the washing step.

Other tips for expediting washing:

• Mark the desired volume on containers used in washing to allow for quicker mixing of detergent, acid, and base solutions.
• Choose the dimensions of any containers used to soak glassware with an awareness of its size and shape to facilitate more efficient processing. For example, in a 12L box (23 x 23 x 31 cm), the glass jars used in the MMA test protocol are most efficiently packed in layers in an alternating “head to toe” orientation.
• Glass vials used in the Oddy test can be time-consuming to clean when pipetting solutions in/out of each vial individually. To empty multiple vials more quickly, hold several in a gloved fist and firmly shake them out over a sink, releasing the liquid all at once. Residual solution can also be drawn out by tapping the open ends against a paper towel or absorbent cloth.

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  Laminated tracking card.

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  Tracking cards used to note the status of acid and base baths.

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  A soaking container marked at 8L volume to expedite mixing fresh solutions.

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  Space-saving “head to toe” packing orientation of glass jars in a 12L (23 x 23 x 31 cm) box.

Tracking Re-Use of Test Components

Sorting reused lids after coupon interpretation.

Tally marks on reused lids in B replicates.

To track and manage the reuse of test components, tally marks can be added to the top of a lid/stopper after each test in which a Temporary rating is assigned. Labeled buckets or beakers can also be used to sort and contain components with the same number of tally marks. It’s recommended to limit the reuse of components with tally marks to B replicates. Any reused components should be noted in the Oddy testing record.

Workflows for Coupon Photography

The Metropolitan Museum of Art (MMA) and Smithsonian National Museum of the American Indian (NMAI) have each developed imaging workflows for coupon documentation using diffuse and glancing-angle lighting. Diffuse lighting allows for proper color representation in the photograph, while glancing-angle lighting allows for the representation of surface texture. The MMA setup utilizes a self-built rigid frame, while the NMAI setup makes use of a modified photo studio setup.

Rigid Frame Set up (MMA)

Using the MMA workflow, Oddy test coupons are photographed using a Rosco LitePad HO90 12”x12” for diffuse lighting, and a Cree XLamp CXA3050 LED with a Mean Well HLG-100H-36A power supply for glancing-angle lighting. Coupons are placed on an angled stage in between the Rosco LitePad and a white piece of paper board used to diffuse light. A photograph is taken in each lighting condition, and photographs are color-corrected and processed in adobe Lightroom. The MMA’s rigid frame setup is illustrated with photographs here. More detailed instructions for construction and use are underway.

Modified Studio Set up (NMAI)

Equipment:

• Caddy for coupons (blueboard tray with gray photo paper wrap)
• AIC color checker (small size)
• Paper labels to identify material
• Gray photo paper
• Blue painters’ tape
• Diffuse light source (Broncolor Minipuls C80 with softbox, or equivalent)
• Full blotter sheet with hole cut for camera
• Glancing angle light source (Broncolor Minipuls C80 with frosted bulb cover, or equivalent)
• DSLR Camera (Nikon D7500, or equivalent)
• Lens (Nikkor 60mm, or equivalent)
• Flash sync unit (hot shoe attachment)

Prepare Photo Setup – Table and Coupons 1. Lay down gray photo paper on table, attach with blue painters tape 2. Secure coupon caddy to gray paper (loop of painters tape on back) 3. Secure AIC color checker to top of coupon caddy 4. Apply appropriate paper label with material ID to label insert 5. Add coupons to caddy 6. Apply P/T/U designation below coupons

Prepare Photo Equipment 1. Camera – Nikon D7500 with 60mm lens a. Format: RAW b. Exposure mode: Manual c. Focus mode: Manual d. Lens: Manual e. ISO 200 f. Shutter speed: 1/200 sec g. F-stop: f/10 h. Distance from table to lens: ~28.5cm

• Insert flash sync unit to hot shoe
• Mount camera to camera stand; using a level, make sure the camera is flush with table and coupon caddy
• Measure distance from lens to table – should be ~28.5cm (11”)
• Attach camera to power source, tether with USB
• White Balance – keep on auto

2. Broncolor lights a. Power: Set dials to 1/8 b. Diffuse light source: 48.5cm distance from caddy c. Glancing angle light source: distance: 84.5cm; angle to caddy should be ~30°

• Diffuse light source: mount Broncolor Minipuls C80 head to UV light stand; collapse stand all the way down, attach soft box to light
• Place light along short side of table with softbox resting on table, ~48.5cm distance from caddy
• Secure the blotter paper to the table with painters’ tape along its short side – opposite the diffuse light source, just next to the edge of the gray photo paper (~3” from caddy)
• Hook the paper over and above the caddy, securing the paper through the hole around the camera lens

• Glancing angle light source - mount Broncolor Minipuls C80 head to UV light stand; adjust stand so light source is ~ 30° angle to the caddy (attach yarn to side of caddy and side of light source – measure angle with angle locator device); distance from light to caddy should be: 84.5cm

Image Capture and Processing

• Capture images in RAW (convert to TIFF when all images are captured).
• Use tethering to capture (Camera Control Pro) .
• With lights on, manually focus the lens on the coupons (*select shutter priority to use the Live View function but be sure to switch to Manual before capture)
• Make sure flash sync is connected to the appropriate lighting source (*the other lighting source should be turned off)
• Capture image and then open in Camera Raw to check focus, exposure and white balance.
• Once the image is successfully captured, switch to the other lighting setup. Connect the flash sync to the other light source, turn on light source, turn off first light source. *Blotter paper should be attached to the camera for the diffuse lighting but detached and curled down for the glancing angle lighting).

Locating a contaminant in the test

Highly abnormal corrosion products on a copper Control coupon, indicating the presence of a contaminant in the Oddy testing setup.

Oddy testing is often conducted in multi-use workspaces shared by multiple users. Despite good lab hygiene and management of equipment, contamination of test components or material samples can occur. The strongest indicator of a contaminant in the test setup is abnormal corrosion on the control. A contaminant in the sample may be indicated by dramatically different test results obtained for the same material at different times, or by different testers.

In the event of contamination in the test setup, a series of investigations may be performed to isolate the affected component(s). Porous, organic test components like sintered nylon coupon hangers, stoppers, o-rings, and lids are thought to be most vulnerable to absorption of compounds from their environment, so it may be appropriate to make them the focus of initial investigations. Tests (without sample material) can be prepared in which one component (lid, stopper, o-ring, coupon hanger) of each test is replaced with new supply from outside the lab. A lack of abnormal results in any test suggests that the contaminated component has been replaced. If all tests still present abnormal results, or the contamination of multiple components is suspected, the opposite approach may be applied, conducting tests in which all components but one are replaced from new supply. If unsuccessful, testing can be expanded further to include metal foil sheets, deionized water inside glass vials, solvents used in coupon preparation, and even glassware as a potential carrier of contaminants introduced in washing.

Tips for specific test protocols

A pair of jar pliers (left) and a strap wrench (right).

Two people work together to open a tightly sealed Oddy test assembly with two pairs of jar pliers.

MMA Method

Releasing tight lids

Some testers using this method have observed that when Oddy tests are removed from the oven, a great deal of effort is occasionally required to open them. This issue is attributed to minor inconsistencies in lid manufacturing. To safely open these difficult test assemblies, some additional tools are helpful. One can use two pairs of jar pliers, one to grip and twist the lid, and the other to rotate the jar in the opposite direction. Alternatively, a strap wrench may be used. In lieu of these tools, and as a final resort, a jar may be wrapped in duct tape, adhesive-side out, with one person holding the jar while a second person twists the lid open. This option should not be exercised without the protection of thick work gloves.

Sourcing alternate lids

IMA/W and BM Methods

Test Contamination Attributed to Silicone Stoppers

Some testers using protocols with silicone stoppers have observed that tests have returned compromised control results - notably a reddening of the copper coupons. This suggests an undesirable contaminant in the stopper itself. Results from a contaminated test can be difficult or impossible to interpret. If corrosion in the control is limited to one coupon, it may be possible to assign results as usual to the other unaffected coupons; and to the affected metal as long as it is worse than the control. However, in the long run, superior silicone stoppers should be sourced. According to conservation scientist Greg Smith, characteristics to look for when sourcing silicone stoppers include a good, snug fit into the test tube, and autoclavability. Stoppers should also be water clear (i.e. no colorant to contribute impurities to the test system), and cured with a platinum catalyst (as opposed to a peroxide catalyst).

Testing New Silicone Stoppers

When considering a new type of stopper, one can evaluate potential alternatives using the Oddy test itself, as long as one has held back some approved stoppers from the previous batch. It’s recommended to keep at least 6 stoppers for this purpose. Test new stoppers in duplicate as you would any material, using 2g samples. Assess the test according to your normal institutional procedure. Reject any batches that rate Temporary or Unsuitable.