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Any analysis of paint materials applied to surfaces must be wary of possible confounding due to the composition of, and reactions with, the substrate. Heavy metals and toxic compounds can be found in paint substrates and a number of examples are listed.

19.1 Putty

Materials for filling cracks in timber, knots and nail holes as well as for sealing glass to window frames has frequently contained lead. Examples of recipes for putty are:

50 pounds Whiting 4 pounds White Lead 1 gallon Raw Linseed Oil

40 pounds Whiting 4 pounds Litharge 2 pounds Patent Dryers 1 gallon Raw Linseed Oil

50 pounds Whiting 8 pounds Litharge

2 pounds Dryers No.1 [Atlas Chemical Company, Sunderland, 1896, p.154-155]

Vanderwalker (1944, p.181) notes the need for soft porous putty to be used in soft porous materials and the putty to be used on hard dense surfaces should have similar properties. Hard plaster finishes and metal window frames are therefore likely sites where putties hardened with white lead may be found. A common putty made from marble dust is described as becoming hard and brittle and (p.182) as being made better with the addition of '...a little white lead, paste or dry white lead...'.

Vanderwalker (1944, p.181-184) describes a range of putty mixtures that contain white lead, including Knifing Putty, Quick-Setting Putty and First Class Putty. In addition a putty made from paint mixed with whiting is described as being good for fillings on the next to last coat of flat wall paint, the paint used in such a putty would generally have been a lead-based paint (p.182a).

In relation to cracks in timber weatherboards, Brindley, (c. 1952, p.54) suggests the use of a '...linseed oil putty or a mixture of this putty and a little paste white lead.' and in relation to picket fences suggests '...A mixture of white lead and linseed oil putty will make a more durable stopping to fill up the open joints'. (p.59).

In describing the use of putty for glazing work, Holloway, (1953, Vol.I, p.69) notes that:

'...Ordinary linseed-oil putty is not particularly satisfactory for metal sashes, for which it is generally too soft. There are a number of proprietary brands of putty for this purpose or ordinary linseed-oil putty can be adapted for it by adding approximately 1 oz. red lead to every 1lb. of putty; the red lead should be of the "jointing," not the "non-setting," type.'.

And when describing puttying in surface filling (page 158):

'For nailholes and similar defects in everyday work, the form of putty most popular among painters is ordinary linseed-oil putty. It is cheap, easy to use, and sufficiently plastic to accommodate itself to subsequent movements of the wood, but it cannot compare with hard putty, made from paste white lead, whiting japan, gold size, and turpentine or mineral spirits.

…...If desired, a little red lead can be added to the mixture to harden it and speed up the drying.'

And as part of the putty recipe, (Vol.II, p.57) a ratio of two thirds ordinary putty to one third white lead in oil is specified.

An Australian source (DLNS , 1955, p.28) notes the use of red lead '...as the principal ingredient in putties, when considerable tenacity and durability are required.'

The history of use of white lead and red lead in putty to fix window glass in place is poorly

documented. It is likely to have been the material of choice at some time and in some situations by some individuals in residential glazing work. Ingestion of lumps of failed old 'window' putty,

containing white lead or similar chipped-out putty from glazing repair would be a source of severe child lead exposure. Glazing putty, being on the outside of window frames, may contribute lead to the soil around the house when it fails. The contribution of lead from putty, to the window well, internal window sill and house dust should also be considered.

PCB has been used in caulking compounds, and as sealants in buildings (Mandyczewsky, 1992) amongst other products.

19.2 Wood preservatives

Timber preservatives include, creosote, coal-tar derivatives, pentachlorophenol, copper chrome arsenate, copper chromate, copper sulphate, zinc chloride, zinc sulphate, mercuric chloride and copper naphthenate (Soong, 1993, Holloway, 1953). An example of a former white ant spray formulation is:

1lb arsenate of soda to 4 gallons of warm water (Mayes, 1938, p.310).

Such compounds could occur in timber being sampled for paint investigations.

19.3 Wood

Some timbers shed paint more rapidly than others and paint failure can be attributable to the timber substrate.

The durability of painted timber is described in Hess (1965, p.303) as follows:

The woods which hold paint longest and suffer least when repainting is neglected are:

(i) cedar, redwood and cypress;

(ii) next in order are northern white pine, western white pine and sugar-pine;

(iii) the third group in order is Ponderosa pine, spruce and hemlock;

(iv) the last group consists of woods which have the poorest paintholding properties: Douglas fir, western larch and southern yellow pine.

and Five factors significantly affect the serviceableness of exterior paints on wood:

(1) the kind and quality of the wood;

(2) the effectiveness of the design of the building or structure in keeping the wood dry enough to hold paint;

(3) the composition and quality of the paint;

(4) the technique of application and programme of maintenance; and (5) the severity of the climate and local conditions of exposure.

Resin exudation, knots and differential physical properties of soft wood and hard wood are some of the intrinsic problems with timbers and their paint holding abilities. British Columbian pine (Oregon and Californian pine or Douglas Fir) is noted as having resin exudation problems and poor paint holding properties (Hess, 1965, p.303). For more local knowledge, a bibliography, 'The paint holding of Australian woods' by Rischbieth, J.R., (1957), available from the National Library of Australia, is suggested.

German standards (Hess, 1965, p.304) DIN 18363 & 55925 stipulated that timber being painted should not contain above 15% water, a condition that may be difficult to achieve in tropical settings or in winter.

19.4 Corrugated iron

Galvanised iron is a source of zinc oxides, zinc chlorides, basic zinc carbonate and perhaps finally iron oxides when weathering takes place. The degree to which cadmium and perhaps traces of lead may be associated with older galvanising, should be considered. The association between cadmium and zinc in ceiling dust from houses with galvanised iron roof materials is demonstrated in van Alphen (1992, p.66).

New sheets of iron have in the past been left to weather to a dull surface before painting owing to difficulties of adhesion resulting in extensive paint flaking.

The difficult adhesion of coatings on new galvanised iron sheets is believed to be due to the formation of a very fine skin of basic zinc chloride, remaining from the use of ammonium chloride, etc., in the galvanising process. (Edwards and Buschlinger.) Also other residues of chemicals and greasy impurities, e.g. palm oil, form a thin layer on hot galvanised zinc sheets and may impair the adhesion of coatings. Other chemicals e.g. trisodium phosphate and solutions of caustic soda, are used for cleaning the sheets, also acid fluxes. [Hess, 1965, p.257]

Calcium plumbate was a common primer for galvanised iron, and red lead is often used to paint between overlapping segments of adjacent sheets.

Hess (1965, p.257) notes the corrosion of zinc as 10-15 times less than for steel, at 0.2oz (avoirdupois)/sq.ft./year in industrial atmospheres, this being some 61 grams/m²/year. In rural locations the rate of corrosion is interpreted as being of the order of 15 to 30 grams/m²/year. It is stated that in enclosed and polluted locations such as railway tunnels, zinc may corrode as fast as steel.

Reactions between zinc and other materials are noted; 'If on account of extraordinary chemical or electrolytic influences, e.g. by contact with nobler metals, a strong corrosion of the zinc has taken place, the layer of white zinc salts formed is sometimes called "white rust". It consists mainly of basic zinc carbonate.' (Hess, 1965, p.258). White salts are commonly seen on the overlapping join areas of sheets of corrugated iron, particularly in coastal settings.

19.5 Paint failure on cement

The compatibility of some paints with particular substrates may be a guide in relation to paint failure or likely presence or absence of pigment. Salt damp related paint failure should be able to be readily discriminated from paint incompatibility with the substrate owing to the localisation and visible salt in the case of salt damp. The compatibility of pigments with Caustic alkali or lime in substrates such as cement, plaster and brickwork, are shown in Table 35.

Table 35: Effect on pigments applied to cement, plaster and brickwork. (Hess, 1965, p.336)

Affected Generally compatible

Inorganic Chrome Yellows

Chrome and Molybdate Chrome Oranges and Reds (there may be some grades unaffected).

Chrome (Brunswick) Greens.

Carbon Blacks, Iron Oxide Blacks and Graphite Iron Oxides (Reds, Browns, Yellows),

Earth Colours (Ochres, Umbers, Sienna, etc.).

Cadmium Yellows, Oranges and Reds (Cadmium/Selenium colours).

Antimony, Titanium and Zinc Whites, Lithopones.

Extenders: Asbestine, Barytes and Blanc fire, Kieselguhr, Silica.

Organic*

Azoic Toners, e.g. Manganese, Calcium and Barium toners of Azo Reds B, 2B and 4B.

Manganese Calcium and Barium B.O.N. Toners.

Maroon Toners (e.g. Manganese).

Organic*

Nickel Azo Yellow.

*organic pigments containing elements which may be used in characterisation of other organic pigments are not listed here.

19.6 Miscellaneous

Timber glues have been known to include lead (Atlas Chemical Company, 1896, p.189-190).

The use of lead fillers and molten lead for car panelbeating resurfacing (Browne, 1983) is likely to have been a source of lead contamination in relation to car finishing in addition to any lead in paint.

It would appear that in Detroit at least in the 1930s that some 80lb of lead was used in the bodywork of a new car (Hunter, 1957), later reduced to 5lb.

On occasion paint embrittlement can be attributed to the substrate:

Many oil varnishes and paints exhibit insufficient adhesion to lead and leaded surfaces, particularly cold- and hot-water pipes, leading to flaking because of the catalytic action of the lead and lead oxides (intentionally made use of in driers) on the drying of oils. This favours the drying of the films, but as the action continues after the drying, the ageing of the film is accelerated and the films embrittle within a comparatively short time. This is certainly not the only reason. For instance bad adhesion to cold-water pipes made of lead or other metals can often be attributed to a film of condensed moisture usually encountered on such surfaces.

[Hess, 1965, p.262]