# Violin Varnish and How to Make It/Chapter 3

CHAPTER III.
Oils.
Among their many and varied properties, oils have the capacity of marking paper in a greasy fashion, different oils doing so in varying degree of persistence. In this manner we are able to distinguish broadly between oils and the kind known as essential oils.
There is another class, which is not much more than a modification of the first—namely, Siccative oils.
The name Siccative is given to a certain class of oils which are produced by other oils coming into contact with air and, by absorbing the oxygen, acquire the property of drying rapidly.
Linseed oil is naturally siccative, but the process of dessication is exceedingly slow, and commercially the property is of not much value.
​Chemistry has, however, been called into operation, and, by various processes, oil can be rendered siccative in a very short time, and so enables us to make use of it in the manufacture of varnish.
Linseed oil is not soluble in water, very slightly in alcohol, but can be dissolved in ether and essential oils.
If prepared by the cold process it is a light yellow colour, and if prepared by heat it is brown yellow.
In common oil, there is often a solution of oils of resin, and such oils must never be employed if good results are to be obtained.
The quality of oil depends completely on the nature of the seed from which it is extracted.
A good oil is very liquid and transparent, and is practically odourless.
Viscous and strong smelling oils are the result of using seeds of inferior quality, or those not fully matured.
Oils as usually obtained in the trade are seldom pure, they generally contain colouring matter, and are otherwise adulterated, therefore only those of the very best quality must be used.
​When oil has been kept for a long period it loses many of its impurities, and when buying it always enquire as to the age, as the older it is the better.
With the aid of chemistry we are able to render oil siccative in a very short time. The process need not be entered into fully at present, but the most usual method is to heat it in the presence of various metallic oxydes.
The mere fact of boiling oil will to a certain extent make it siccative, but if boiled together with some litharge it will become more siccative still, while similar treatment with oxide of manganese will impart a high degree of siccativity to the oil.
The oils in which oxygen is most intimately combined, in which the admixture of metallic oxides dissolved therein is the most perfect, and which contain the smallest amount of moisture, are the only ones that should be used for the purpose of making varnish, as the success of the varnish depends chiefly on the quality of the oil in its composition.
The distinctive character of Essential Oils ​is that while it will mark a piece of paper in a greasy fashion, the mark is not permanent, but will in a certain time entirely disappear, and, under the influence of heat, disappear more rapidly.
They have the property, as have certain other oils, of becoming solidified and leaving a deposit of rosin.
Technically, there are many varieties of these oils, which are all duly classified, but for our purpose we can divide them into two broad classes–those that remain liquid and those that can be solidified in the form of crystals.
They are hardly soluble in water, though they impart to it its odour.
NOTE. I have throughout used the word drying, because it is the usual expression. As a matter of fact oil does not dry at all, but becomes solid by contact with the oxygen in the air, and clings permanently to the surface to which it is applied.