Ordinary white paint is generally composed of white lead, linseed oil, driers, and spirits of turpentine.

A coloured lead paint is produced by adding a pigment to the above.

In the mixture each constituent plays a part.

The oil soaks into the pores of the material painted, and then dries into a resinous compound, keeping out the air, and preventing decay.

The drier causes the oil to oxidise and solidify more quickly.

The white lead gives body and opacity to the mixture. It does not merely mix with the oil, but combines with it to form a creamy compound which dries into a soapy substance.

The spirit of turpentine is merely a solvent added to make the paint work more freely; it eventually evaporates and plays no permanent part.

Proportions Of Ingredients

The exact proportion of the ingredients best to be used in mixing paints varies according to their quality, the nature of the work required, the climate, and other considerations.

The composition of the paint for the different coats also varies considerably.

The proportions given below must therefore only be taken as an approximate guide when the materials are of good quality : -

Table showing the Composition of the different Coats of White Paint, and the Quantities required to cover 100 Square Yards of New "Wrought Deal

Red lead.

White lead.

Raw linseed oil.

Boiled linseed oil.

Turpentine.

Driers.

Remarks.

Inside Work.

4 coats not flatted.

Lbs.

Lbs.

Pints.

Pints.

Pints.

Lbs.

Priming .

1/2

16

6

...

...

1/4

Sometimes more red lead is used, and less drier.

2d coat

*

15

3 1/2

...

1 1/2

1/4

* Sometimes just enough red lead to give a flesh-coloured tint.

3d coat

...

13

2 1/2

...

1 1/2

1/4

4th coat .

...

13

2 1/2.

...

1 1/2

1/4

Inside Work.

4 coats and flatting.

Priming .

1 1/2

16

6

12

1/8

Some painters make these coats of the same composition as those for non-flatted work.

2d coat

...

12

4

1 1/2

1/10

3d coat

...

12

4

...

0

1/10

4th coat .

...

12

4

0

1/10

Flatting .

9

0

...

3 1/2

1/10

Outside Work.

4 coats not flatted.

Priming .

2

18*

2

2

...

1/8

When the finished colour is not to be pure white, it is better to have nearly all the oil boiled oil. All boiled oil does not work well. For pure white a larger proportion of raw oil is necessary, because boiled oil is too dark.

2d coat

...

15

2

2

1/2

1/10

3d coat

...

15

2

2

1/2

1/10

4th coat .

....

15

3

2 1/2

0

1/10

For every 100 square yards, besides the materials enumerated above, 21/2 lbs. white lead and 5 lbs. putty will be required for stopping (see Part II. p. 413).

The area which a given quantity of paint will cover depends upon the nature of the surface to which it is applied, the proportion of the ingredients, and the state of the weather.

When the work is required to dry quickly, more turpentine is added to all the coats.

In re-painting old work, the surface (after the necessary preparation, see Part II.) is considered as if it were primed. Only two more coats are generally applied, of which the first is called the second colouring; a fourth coat is seldom required. The second and third coats contain equal parts of oil and turps; all the remaining ingredients are as shown in the Table above.

For outside work exposed to the sun, the second and third coats each contain 1 pint turpentine and 4 pints of boiled oil, the remaining ingredients being as stated in the Table. The extra turpentine is introduced to prevent blistering.

In cold weather more turps is used to make the paint work freely.