Material Which is Compatible with an Artefact

Definition:

A material which is compatible with artefact may not be absolutely inert, but its instability or the products it gives off may not represent a danger to the artefact with which it is used. Care must always be taken to ensure that the materials are compatible with the artefacts and that the artefacts are compatible with one another.

The compatibility of material with artefacts depends of the following variables:

Museum objects:

- nature of artefacts
- age and condition

Material:

- nature of material (chemical composition)
- concentration of chemical products
- age of material
- surface of the material (m²)

Context:

- proximity of the artefact and the material
(contact or non-contact)
- air tightness of the environment
(open or close system, ventilation and dimension of the system)
- duration of living together
- physio-chemical conditions:

- cleanness of the artefact
- relative humidity
- temperature
- ultraviolet and visible radiation

There are no absolutes. Whenever possible,
discuss your plans with a conservator

Wood

Problem with wood:

- acids are released that may damage objects

General rules:

- no wood is perfect
- avoid direct contact between wood and objects
- substitutes:

- metal with powder coating
- galvanized and stainless steel
- acrylic or glass

Acidity of different wood species.

* A single type of wood may display a very wide pH range, e.g. European beech varies between pH 7.2 and 3.9. This variability can be attributed principally to sampling and the different experimental set-ups of various authors.

Wood Panel Products:

Problems:

- emission of organic acids from the wood
- emission of formaldehyde and acid from the adhesives
- there is less control over the wood species used

General rules:

- use the best type of adhesives (e.g. exterior grade)

Best:

- overlaid plywood and plastic-laminated panels

(These products reduce or stop the release of volatile compounds from panel faces.
Panel edges release volatile compounds and should be sealed.
Order with the colour that you want.
Specify without urea formaldehyde.)

- plywood with phenol formaldehyde impregnated paper overlays

- High Density Overlaid (HDO) plywood - stops emissions
(e.g. Permaply HDO; Duraply HDO)
- Medium Density Overlaid (MDO) plywood - reduces emissions
(e.g. Permaply HDO; Duraply HDO)

- plywood with phenolic laminates - stops emissions
(e.g. Arborite; Formica)

- particleboard with factory applied Melamine laminates
(some colour selections available)

- unlaminated panels

- exterior grade plywood
- particleboard without urea formaldehyde adhesives
(e.g. Medex with polyurea; and other exterior grade particle boards)

Worst:

(These tend to emit volatile compounds harmful to artifacts).

- interior plywood
- interior particleboards
- waferboard
- chipboard
- untempered hardboard (e.g. Masonite, Isorel)
- oil tempered hardboard (e.g. tempered Masonite)
- fiberboards

Papers and Cardboards

Problem:

- acids and peroxides released may damage objects

General Rules:

- choose products that are labelled acid-free
- substitute:
- non-woven, spunbonded, polyethylene (PE) sheeting (Tyvek)

Best:

- acid free tissue paper
- archival quality papers (e.g. Permalife paper)
- acid-free mat board
- acid free corrugated paper board
- acid free folder stock (e.g. Perma/Dur)
- acid free honeycomb paper panel

Worst (acidic products):

- news print
- Kraft paper
- cardboard
- glassine
- wrapping paper

Coatings: Paints, Varnishes and Stains

Problems:

- efficiency as a barrier to volatile compounds is variable from product to product
- release organic acids, peroxides, formaldehyde, etc. at different rates

General Rules:

- avoid direct contact between coating and objects
- let dry at least one month before using (requires good ventilation)
- avoid:

- oil-based paints; alkyd paints
- oil-modified polyurethane varnish

- no coating is a complete barrier but vapour barrier character increases with each layer applied
- substitutes for coatings:

- avoid use of materials that require use of vapour barriers
- aluminum foil barrier sheeting: completely impermeable if not damaged
(e.g. Marvelguard; Marvelseal)

For more information on the use of coatings for museum purposes, refer to CCI =s Technical Bulletin 21 Coatings for Display and Storage in Museums (Tétreault 1999). Visit the CCI online Bookstore for more information.

Table 1. Classification of coatings and summary of coating recommendations.

Classification of Coatings by Film-forming Mechanism
Class Solvent evaporation (SE): Coalescence (C): Oxidative polymerization (OP): Moisture-cured polymerization (MC): Catalysed polymerization (CP): Change-of-phase (CoP):				Examples shellac, cellulose nitrate emulsion, latex, water-based oil, alkyd, epoxy ester, oil-modified urethane moisture-cured urethane two-part epoxy, two-part urethane powder coatings
Summary of the Coating Recommendations
Legend and notes: DP, drying period; w, week; d, day; AE, air exchange rate; à, should not have components formed by oxidative polymerization; , high amount of calcium carbonate is preferable; , varnishes need more layers; +, drying period will vary depending on the ratio of the coated surface to the volume of the enclosure.
	Wood products	DP	Metal	DP	Cementious subst.	DP
Airtight enclosures (AE »1/day)	epoxy CP, CP+C	4w	all films CoP	1d	epoxy CP, CP+C	4w
	urethane CPà	4w	epoxy CP, CP+C	4w	Urethane CPà	4w
	all films Cà,	4w	Urethane CPà	4w	all films Cà	4w
	shellac SE	4w	acrylic C	4w
Leaky enclosures+ (AE» 10/day)	epoxy CP, CP+C	2-4w	all films CoP	1d	epoxy CP, CP+C	2-4w
	urethane CPà , MC	2-4w	baked alkyd OP	2-4w	urethane CPà, MC	2-4w
	shellac SE	2-4w	epoxy CP, CP+C	2-4w	all films Cà	2-4w
	all films Cà,	2-4w	urethane CPà	2-4w
			acrylic C	2-4w
Open enclosures (AE»100/day)	epoxy CP, CP+C	4d	all films CoP	1d	epoxy CP, CP+C	4d
	urethane CP, MC	4d	baked alkyd OP	4d	urethane CP, MC	4d
	all films SE, Cà	4d	epoxy CP, CP+C	4d	all films Cà	4d
			urethane CP	4d
			acrylic C	4d
Floors (AE »100/day)	urethane CP, MC, C	4d	all films CoP	1d	urethane CP, MC, C	4d
	epoxy CP, CP+C	4d	baked alkyd OP	4d	epoxy CP, CP+C	4d
	acrylic-urethane C	4d	urethane CP	4d	acrylic-urethane C	4d
			epoxy CP, CP+C	4d
Contact between objects and film	interleaves	4d	interleaves	4d	interleaves	4d
	all filmsà	4w	all films CoP	1d	all filmsà	4w
			baked alkyd OP	2w
			unbaked filmsà	4w

Plastic Products

Problems:

- some plastics release harmful degradation products
and additives such as plasticizers (phthalate)

General Rules:

- do not use chlorine-containing compounds, e.g. poly(vinyl chloride) (PVC); chlorinated rubbers or rubbers containing sulphur vulcanizing agents
- choose acid-free products
- choose:

- polyethylene (PE)
- polypropylene (PP)
- polyester (poly(ethylene terephthalate)) (PET)
- polystyrene (PS) and modified PS such as:

- acrylonitrile/butadiene/styrene (ABS)
- high impact polystyrene (HIPS)

- acrylic
- polycarbonate
- polytetrafluoroethylene (PTFE)

Sheet Plastics

General Rule: The efficiency of the vapour barrier increases with the thickness.

Best:

best barrier:

- aluminum foil barrier sheeting (e.g. Marvelseal; Marvelguard)

good barriers:

- acrylics (e.g. Acrylite SDP; Plexiglas)
- polycarbonate (e.g. Cryolon SDP; Lexan; Tuffak)
- air-bubble sheeting (e.g. Aircap; Astro-bubble; Bubble Pack; polyCap)
- polystyrene crystal; food grade
- polytetrafluoroethylene (PTFE) (e.g. Teflon)
- silicone

substitutes:

- glass
- Denglas (non-reflective glass)
excellent barrier:
- poly(vinylidene chloride) (e.g. Saran)
(potential problem with Chloride)

Worst:

- poly(vinyl chloride) (PVC)
- rubber with sulphur vulcanizing agents
- chlorinated rubber
- cellulose nitrate
- cellulose acetate

Foams

Best:

- polyethylene (PE) (e.g. Ethafoam; Polyplank; Polyfoam)
- cross-linked polyethylene (e.g. Plastazote; Volara)
- white, extruded plank (not expanded bead) polystyrene (e.g. Styrofoam)
- ethylene/vinyl acetate copolymers (EVA foam) (e.g. Evazote; Volara)
- polypropylene (e.g. Microfoam)
- silicone

Worst:

- polyester polyurethane foam (commonly called polyester foams)
- polyether polyurethane foam (commonly called polyurethane foam)
- chloroprene (e.g. Neoprene)
- poly(vinyl chloride) (PVC)
- rubber with sulphur vulcanizing agents

Plastic or Foam Boards

Best:

- corrugated plastic boards (Coroplast; Cor-X; Hi-Core; PolyFlute; Kortek)
- paper-faced, laminated panel board (ArtCor; Fome-Cor)
- styrene plastic faced laminated panel board (ArtCor)
- aluminum sheet laminated to panel board

Worst:

- urea formaldehyde impregnated paper laminated panel board (Gatorfoam)
- polyurethane foam board
- poly(vinyl chloride) (PVC) foam boards (e.g. Sintra)

Wires and Tubes

Best:

- Nylon monofilament (fishing line)
- polyester monofilament (fishing line)
- polyethylene (PE) plastic-coated wire
- polyethylene (PE) or silicone tubing
- polytetrafluoroethylene (PTFE) (e.g. Teflon)
- glass tubing

Worst:

- poly(vinyl chloride) (PVC) tubing (e.g. some Tygon)
- rubber tubing with sulphur vulcanizing agents
- chloroprene rubber (e.g. Neoprene)

Adhesives and Tapes

Problems:

- components of adhesives may be transferred to objects
- adhesives may embrittle, ooze, yellow, become acidic

General Rules:

- wait at least one month before putting object in a closed system
to allow for the evaporation of any solvents.
- avoid direct contact between adhesives and objects
- substitutes:

- mechanical fastening are preferable then adhesives
(e.g. nails, screws, Velcro)

Best:

- certain acrylics
(e.g. Acryloid F-10; Acryloid B-72; Acryloid B-82;
Rhoplex AC-33; Rhoplex AC-234)
- transparent acrylic adhesive on polyester tape carrier
(e.g. Scotch Brand Tape #415)
- acrylic contact cements
- certain two-part epoxies
(e.g. Epo Tek 301-2; Hxtal NYL-1)
- certain poly(vinyl acetate) (PVA) emulsions
(e.g. Jade No. 403; R-2258; Mowilith DMC2)
- certain ethylene/vinyl acetate copolymers (EVA)
(e.g. Beva 371)
- certain hot melt glues
- animal glues (may stain)
- starch paste (rice; wheat)

Worst:

- most epoxies
- polysulphides
- most poly(vinyl acetate) (PVA) emulsions and solids
(e.g. sure-Grip;CM Bond M-2; Bulldog Grip 20 minute resin)
- cellulose nitrate (e.g. Glyptal)
- natural and synthetic rubber cements (most contact cements)

Textiles

Problem:

- may have finishing treatments that compromise their inherent qualities

General Rules:

- avoid wool products (sulphur-containing protein)
- colour fast to water, solvents and crocking
- wash fabrics before using
- use undyed, unbleached fabrics for storage and packing
- use non-fading fabrics in exhibits

Best:

- unbleached cotton and linen
- polyester: woven, spunbonded (e.g. Hollytex; Reemay)
- nylon: woven and spunbonded (e.g. Cerex)
- acrylic (e.g. Decofelt; Orlon)
- hook and loop fasteners (Velcro)

Worst:

- wool (tarnishes silver)
- fire retardant treatments (disodium phosphate, etc.)
- durable press finishes (urea formaldehyde)
- carpets: generally accumulate dust and can house insects
- carpets with rubber based backings

Miscellaneous

Best:

- glass
- ceramics
- neutral silicone sealant (e.g. Dow Corning 795; Silicone GE II)
- rubber sealants without sulphur vulcanizing agents
(non-contact) (use after 1 month)
- metals (avoid galvanic corrosion)
- pen with acid-free indelible ink (e.g. Pigma Pens)

Worst:

- cellulose nitrate
- sand, soil and pebble (contact with salts)
- acidic silicone adhesive and sealant

Pesticides

Problems:

- content of corrosive agents, solvents and other volatile compounds
that are harmful to objects

General rules:

- no contact with object (no sprays)

Best:

- low temperature
- Bendiocarb (Ficam)
- fumigation with:

- inert atmosphere (N₂; CO₂; Ar)

Worst:

- fumigation with:

- Chloropicrine
- Dichlorovos
- phosphine

Control of Volatile Compound Levels and Pollutants

- activated charcoal (6 to 14 Mesh or 1.4 to 3.4 mm)
- silica gel
- anti-tarnish cloth or paper
- copper, zinc or silver compounds (e.g. Pacific Silvercloth)
- oxygen absorber (e.g. Ageless)
- wrap object and limit access
e.g. unbleached cotton, acid free tissue, polyethylene, poly(ethylene terephthalate) (Mylar)