September 23, 1871.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
253* 
IpmecMup jof Scientific S0ncti.es. 
SOCIETY OF ARTS. 
Boiled Oils and Varnishes. 
BY CHARLES W. VINCENT, ESQ. 
My chief desire on the present occasion is to render 
as complete an account of the process of oil-boiling by 
steam as I can, without committing any breach of confi¬ 
dence towards those for whom I have been professionally 
engaged. A certain amount of reticence is necessitated 
by this latter consideration, but, at the outset, I may 
state that it applies only to the particular substances 
used to give the necessary drying or solidifying qualities 
to boiled linseed oil, and hence technically termed driers. 
The process itself may be used with any of the substances 
commonly employed in boiling oil by fire for the same 
purpose. The apparatus employed and modus operandi 
being well known throughout the trade, I am rather 
benefiting than injuring the cause of the manufacturers 
by publishing an account of the present state of a mode 
of manufacture which must eventually become the prin¬ 
cipal source of boiled oil. 
The first consideration which presents itself to a prac¬ 
tical man on approaching a subject which he wishes 
thoroughly to master and understand is, What do I want 
to do P the second being, How can I do it ? Viewed in 
this way, it became evident to those engaged in this re¬ 
search that oil-boiling might be reduced to a much 
more simple and perfect operation than that ordinarily 
pursued. 
The principal worker who has published the result of 
his researches is M. E. Ckevreul, who, in 1856, in an 
admirable paper in the Annales de Chimie, definitely 
pointed out that the act of drying of linseed oil is one of 
absorption of oxygen, and consequently might more 
properly be termed solidification than drying (we will, 
however, retain the accustomed term); next, that many 
driers act catalytically; and lastly, that too long boiling 
retarded the drying of the oil. For instance, oil boiled 
three hours without driers, and afterwards three hours 
with litharge, dried more slowly than the same oil 
boiled for three hours with litharge, without any pre¬ 
vious heating. 
To whom the next discovery is due, viz. that the high 
temperature attained in oil-boiling by fire, is unneces¬ 
sary I do not know. I discovered the fact for myself in 
1859-60, when engaged in a research for Messrs. Leigh¬ 
ton Brothers, of the Illustrated London JS r ctvs, on var¬ 
nishes for printing inks; and at that time I introduced 
a mode of steam oil-boiling and varnish making which 
is still carried out by some of the largest makers of 
printing inks and those kinds of varnishes. The fact is 
now very generally accepted, though some manufac¬ 
turers still hold aloof. 
There are reasons which interfere with, and which 
stop the progress of many aids and inventions, though 
against reason, and the oil trade is not free from these 
drawbacks. A principal one is, that the manufacturers 
are in a great measure tied down by the wishes and 
desires of their customers, so that in many cases they 
have to produce rather what the consumers think they 
require than what they really need. It is this multipli¬ 
city of objects which causes the great variety of modes 
of manufacture of linseed oil for painting purposes. It 
is a common case to find that what one person, a large 
consumer, calls a thoroughly good boiled-oil, his neigh¬ 
bour, an equally large consumer, will pronounce entirely 
unfit for use. Now, it is my earnest wish that, as far 
as possible, you should hold yourselves free from pre¬ 
conceived notions of what constitutes a good boiled-oil 
or varnish conventionally, and, considering merely the 
uses to which they are required to be put, reflect how 
far these requirements are met. My own personal ex¬ 
perience has placed certain points before me as of para¬ 
mount importance, and to these I shall direct your atten¬ 
tion. Those characteristics which may be essential to 
the good quality of one mode of boiling oil, but do not 
forward results produced when these articles are applied 
to their various uses, I shall neglect. 
Before entering upon my subject, I must remark that 
no paper read before the Society of Arts on oil-boiling 
and varnish-making can bo complete and appropriate 
without at least some allusion to that communication 
on the subject presented by Mr. J. Wilson Neil, for 
which the Isis Gold Medal was awarded to him in tho 
session 1832-3 of the Society, which was published in 
the ‘ Transactions,’ vol. xlix. part 2. It is not within 
the scope of the present paper to treat of the modes of 
manipulation, recipes, and precautions which he there- 
so fully, carefully, and, indeed, conscientiously describes; 
but the fact remains that that paper was the foundation, 
and remains so to this day, of all tho published accounts 
of modes of manufacturing varnishes. The alterations 
and modifications which have been from time to time 
worked out, are more in the shape of mechanical appli¬ 
ances for facilitating rapidity, easing labour and provid¬ 
ing greater safeguards against fire, than improvements 
of process. The principle of manufacture remains the 
same, and the varnishes now made cannot bo said to be 
better in quality, though they may be made at a less 
cost, and in shorter time, than those produced under the 
processes detailed by Mr. Neil. Many firms still retain 
modes of operation almost (in some cases quite) identical 
with those he describes. The paper is still of such 
value that the Society would, even now, confer a benefit 
on the trade were they to republish it. 
For a process of oil-boiling by fire, Mr. Neil’s is 
nearly perfect; the new process depends on principles- 
entirely different from those he dealt with, and therefore 
it is necessary to begin the subject, as it were, de novo. 
Linseed-oil is boiled for two reasons, as you all know; 
firstly, in order to facilitate its drying when spread 
on thin surfaces, either alone or mixed with paint; 
secondly, that it may serve as a vehicle for the mecha¬ 
nical suspension of the finely-divided particles consti¬ 
tuting a paint; that it may give a certain coliesivo 
power to the mixed paint so constituted, enabling it to 
adhere to tho surfaces on which it is spread, neither 
running into drops, nor leaving the colouring matters 
behind, but carrying the whole of the colour evenly 
diffused through it over the whole surface upon which, 
the paint is laid, and, when dry, forming together a sur¬ 
face which is, as far as may be, impermeable to gases 
and liquids. Technically, these are the two qualities 
which consumers rightly agree in desiring in boiled oil, 
—that it should be a quick-drying oil, and have a good 
body. But it is frequently the case—and, in my opinion, 
they err in so doing—that consumers require in boiled 
oil, besides these two essential qualities, others in reality 
quite adventitious, to which, either from experience of 
some particular sample, from the custom of their trade, 
or from the mode in which they have been led to believe 
good boiled oil alone can be made, they attach a ficti¬ 
tious importance. It is of every-day occurrence that, 
unless the oil complies with these artificial demands, it 
is unhesitatingly condemned, independently oi the t\\ o 
essentials upon which all are agreed.. I or instance, 
some persons attach the idea of a particular smell iO be 
a good sample of boiled oil. If all were agreed as to 
what that smell should be, the desire would be cm mi 
to satisfy; but, taking it for granted that the smell is a 
guarantee that the oil has been heated for a certain time 
at a certain temperature, it is obvious that two samples 
of oil may have that odour, whilst from the different 
ages of the oils previous to boiling, the quality of the 
seed from which they were expressed, or the driers, em¬ 
ployed, their qualities of drying and body may be widely 
different. Other persons, again, confine in their opinion 
good quality to a particular shade of colour and degiee 
