In these oxide of iron (see p. 409) forms the basis. They are free from injurious ingredients such as those of lead paints. For painting iron work they are said to be particularly suitable, on the ground that they do not set up any galvanic action such as is supposed to take place between lead paints and iron surfaces. It is very doubtful, however, whether any such galvanic action exists. When the surface of the iron is rusty, the rust becomes incorporated with the paint.
The paint must, however, be made from the sesquioxide or red oxide of iron. If made from the protoxide it is liable to rust in itself.1
To ensure this power of covering a large area with a small quantity of paint, the ingredients should be reduced to an impalpable powder before they are mixed with the oil. They are ground for seven or eight hours.
Torbay Paint is produced from a brown haematite iron ore found in Devonshire. It contains from 50 to 65 per cent oxide of iron, the remainder being siliceous matter.
This paint has been in use for many years, it is especially suitable for painting iron work, and has borne a high character for durability under exposure to weather and fumes of manufactories.
An official report, quoted in the Manufacturers' Circular, says that "62 lbs. of the Torbay iron paint effectually cover as much surface as 112 lbs. of either white or red lead paint."
There are several inferior imitations of this paint. A great deal of the so-called Torbay paint is, however, nothing more than sulphate of baryta coloured with oxide of iron, whereas sulphate of baryta is never found in the genuine paint in any appreciable quantity.
Black Oxide of Iron Paint is made from the oxide obtained as a bye product in making dyes, ground in oil with about 15 per cent of terra alba, Paris white, or sulphate of baryta. It is said that without the addition of these substances the oxide of iron would set with the oil into a solid mass.
This paint is used for painting shot and shell.
Pulford's Magnetic Paint is made from the magnetic or black oxide of iron.
Purple Brown Oxide is a hydrated peroxide of iron used as a basis for paint.
Silicate Oxide Paint is prepared from an iron ore in Devonshire by the Silicate Oxide Paint Company in three colours only - yellow, red, and black. It contains more oxide of iron and less siliceous matter than the Torbay paint.
1 Proc. Society of Engineers, 1875.
Titanic Paint is made by powdering a black iron ore, which contains oxide of iron and oxide of titanium in nearly equal proportions, mixed with other ores. It is said to harden without the aid of a drier, and to be particularly well adapted for withstanding heat.1
They are sold dry, and require only to be mixed, not ground with oil.
They are used chiefly for external work, "lasting longer than white lead and costing less."
"The original makers of this paint are Messrs. Walter Carson and Sons, and if genuine, as supplied by this firm, it should consist of ground glass and white lead in about equal proportions.
"The rubbish which is frequently sold as anti-corrosion has greatly injured the reputation which this paint at one time possessed. It can be obtained as low as 6s. per cwt., whilst the price of the genuine is from 22s. to 24s. It is not at all uncommon to find anti-corrosion containing from 35 to 45 per cent of sulphate of baryta, a substance which I am assured is never employed by the original makers." l
"An anti-corrosive paint is also made of equal proportions of whiting and white lead, with half the quantity of sand, dust, and any required colouring matter. Being mixed with water, it can be used as a water colour, but is generally applied as an oil paint, the best oil for the purpose being 1 boiled to 12 of raw linseed and 3 of sulphate of lime, all by weight One gallon of the oil will take 7 lbs. of the paint." 2
Enamel Paint consists of a metallic oxide, such as oxide of zinc or oxide of lead, ground with a small quantity of oil, and mixed with petroleum spirit holding resinous matter in solution.1
This paint can be prepared to dry either with a firm glossy surface, like porcelain, or with the appearance of an ordinary flatted coat.
It is about the same price as ordinary paint, but two coats of it are said to be sufficient.
This paint has been extensively employed in the metropolis, and is said to be particularly suitable for surfaces required to be hard and washable; also for those exposed to the action of steam, acids, or alkalies, or to the fumes of gas (see Silicate Enamel Paint, p. 427).
Indestructible Paint is similar to enamel paint in composition and characteristics, except that it contains bitumen and is made in three colours only - viz. bronze-green, chocolate, and black.
Gay's Impenetrable Paint dries quickly with hard enamel face, is very durable, smells less than ordinary paint, and is said to resist heat and damp better. It is supplied ready for use, and is familiar to all as the covering used for the post pillar boxes.
Silicate Paints, made by the Silicate Paint Company, have for their basis a very pure silica obtained from a natural deposit in the west of England. This is levigated, calcined, and mixed with resinous substances.3
3 Phipson, International Congress.
These paints are stated to have no chemical action on metals, to stand 200° heat without blistering, to set quickly and dry with a hard surface, to be indestructible, and, weight for weight, to cover double the surface as compared with lead paint
This paint is sold in the same form as lead paints, and must be used with special "silicate driers."
"The silicate paints supplied by the Silicate Paint Company are highly recommended by the architect of the London School Board for all internal work where health and cleanliness are aimed at." 1
Griffith's Silicate Enamel Paint is stated in the patentee's circular to possess the following characteristics among others : -
It is supplied ready for use; forms hard enamelled surfaces; prevents the corrosion or oxidation of metal; is proof against the penetration of damp; dries rapidly; is not injured by gases, fumes, hot or cold water, soap, or dilute acid; requires no varnish.
One coat is sufficient for waterproofing, but two or more are required to produce a highly-glazed surface. The bulk is about three times that of ordinary paint for the same weight. On metal one gallon will cover 500 square feet; the quantity required to cover other substances depends upon the porosity of the material to be covered.
Silicate Oxide Paint is prepared from an ore in Devonshire in three colours only - yellow, red, and black. It contains more oxide of iron and less siliceous matter than the Torbay paint.
Silicate Alumina Paint is of the same description.
Wood's Compo Paints u are coloured varnishes rather than paints, and very good for outdoor work, containing neither oil, turps, nor driers, and drying rapidly with a bright gloss. They neither crack nor blister in the sun, and one coat on bare iron, stone, or wood is equal to two of ordinary paints." 1
Szerelmey's Compositions are of three kinds: - 1. Stone composition (see p. 79). 2. Iron paints. 3. Liquid enamels.
The Iron Paints of several colours are sold in paste, ground in oil, or in liquid. They are tough and elastic, and prevent or stop rust and corrosion.
They dry in from 24 to 48 hours.
One pound of the paste will cover 4 square yards, and one pint of the liquid 10 to 12 square yards. Two coats are generally sufficient.
This paint was used for the iron roofs of the Houses of Parliament, and is applicable to dry surfaces of iron or wood.
Szerelmey's Liquid Enamels are sold in a liquid state, and are applied with a brush.
They dry in from two to four hours. 1 lb. covers about 4 square yards. One coat is sufficient for iron, two are required for wood.
They can be applied to dry surfaces of wood, iron, tin, whitewash, or plaster.
Granitic Paint is said by the manufacturers to be proof against heat, wet, or frost; to be more durable and cheaper than lead paints; and to be specially adapted for painting or making joints in iron work.
One cwt. of the light colour will cover from 600 to 650 yards, and one cwt. of the dark colour will cover from 1000 to 1200 yards - one cwt. on wood, on stone or iron much more.1
The paint is sold in powder or ground in oil; the latter only should he used for flatting.2
They are also "largely made from the products of coal and other mineral oils.
"They have various degrees of fineness, the cheapest kinds having a great resemblance to tar, and they are admirably suited for painting the inside of pipes, or for iron work fixed under water, such as bridge cylinders and screw piles.
"The fine sorts, while possessing the same properties, give a smoother surface, and can be used in ordinary situations, especially where water or foul vapours have to be resisted.
"The price varies from 18s. to 30s. per cwt., and the paint is mixed for use with specially prepared mineral oil.
"A paint made from bitumen dissolved in paraffin and linseed oils while in a state of great heat, is said to possess special qualities of durability, in that it can resist the action of ordinary detergents, and of all alkalies and acids.
"When mixed ready for use this paint costs from 40s. to 60a per cwt., according to colour and fineness." 3
A paint of this kind is also made by dissolving equal parts of asphalte and resin in common turpentine.4
Champion's Black Paint is a compound of lampblack, mineral matter, and oil.