Experiments and Considerations Touching Colours (1664) by Robert Boyle

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First, That I have often observ'd that Calcin'd Lead Colliquated with fine
White Sand or Crystal, reduc'd by ignitions and subsequent extinctions in
Water to a subtile Powder, will of it self be brought by a due Decoction to
give a cleer Mass Colour'd like a _German_ Amethyst. For though this glass
of Lead, is look'd upon by them that know no better way of making
_Amanses_, as the grand Work of them all, yet which is an inconvenience
that much blemishes this way, the Calcin'd Lead it self does not only
afford matter to the _Amanses_, but has also as well as other Metals a
Colour of its own, which as I was saying, I have often found to be like
that of _German_ (as many call them) not Eastern Amethysts.

Secondly, That nevertheless this Colour may be easily over-powr'd by those
of divers other Mineral Pigments (if I may so call them) so that with a
glass of Lead, you may Emulate (for Instance) the fresh and lovely
Greenness of an Emerald, though in divers cases the Colour which the Lead
it self upon Vitrification tends to, may vitiate that of the Pigment, which
you would introduce into the Mass.

Thirdly, That so much ev'n these Colours depend upon Texture, that in the
Glass of Lead it self made of about three parts of _Lytharge_ or _Minium_
Colliquated with one of very finely Powder'd Crystal or Sand, we have taken
pleasure to make the mixture pass through differing Colours, as we kept it
more or less in the Fusion. For it was not usually till after a pretty long
Decoction that the Mass attain'd to the Amethystin Colour.

Fourthly and lastly, That the degrees of Coction and other Circumstances
may so vary the Colour produc'd in the same mass, that in a Crucible that
was not great I have had fragments of the same Mass, in some of which
perhaps not so big as a Hazel-Nut, you may discern four distinct Colours.

_Annotation VI._

You may remember (_Pyrophilus_) that when I mention'd the three sorts of
adventitious Colours of Metals, I mention'd them but as the chief, not the
only. For there may be other wayes, which though they do not in so strict a
sense belong to the adventitious Colours of Metals, may not inconveniently
be reduc'd to them. And of these I shall name now a couple, without denying
that there may be more.

The first may be drawn from the practise of those that Dye Scarlet. For the
famousest Master in that Art, either in _England_ or _Holland_, has
confess'd to me, that neither others, nor he can strike that lovely Colour
which is now wont to be call'd the _Bow-Dye_, without their Materials be
Boyl'd in Vessels, either made of, or lin'd with a particular Metall. But
of what I have known attempted in this kind, I must not as yet for fear of
prejudicing or displeasing others give you any particular Account.[24]

The other way (_Pyrophilus_) of making Metals afford unobvious Colours, is
by imbuing divers Bodies with Solutions of them made in their proper
_Menstruum's_, As (for Instance) though Copper plentifully dissolv'd in
_Aqua fortis_, will imbue several Bodies with the Colour of the Solution;
Yet Some other Metalls will not (as I elsewhere tell you) and have often
try'd. Gold dissolv'd in _Aqua Regia_, will, (which is not commonly known)
Dye the Nails and Skin, and Hafts of Knives, and other things made of
Ivory, not with a Golden, but a Purple Colour, which though it manifest it
self but slowly, is very durable, and scarce ever to be wash'd out. And if
I misremember not, I have already told you in this Treatise, that the purer
Crystals of fine Silver made with _Aqua fortis_, though they appear White,
will presently Dye the Skin and Nails, with a Black, or at least a very
Dark Colour, which Water will not wash off, as it will ordinary Ink from
the same parts. And divers other Bodies may the Same way be Dy'd, some of a
Black, and others of a Blackish Colour.

[24] See the latter end of the fiftieth Experiment.

And as Metalline, so likewise Mineral Solutions may produce Colours
differing enough from those of the Liquors themselves. I shall not fetch an
Example of this, from what we daily see happen in the powdring of Beef,
which by the Brine imploy'd about it (especially if the flesh be over
salted) do's oftentimes appear at our Tables of a Green, and sometimes of a
Reddish Colour, (deep enough) nor shall I insist on the practise of some
that deal in Salt Petre, who, (as I suspected, and as themselves
acknowledg'd to me) do, with the mixture of a certain proportion of that;
and common Salt, give a fine Redness, not only to Neats Tongues, but which
is more pretty as well as difficult, to such flesh, as would otherwise be
purely White; These Examples, I say, I shall decline insisting on, as
chusing rather to tell you, that I have several times try'd, that a
Solution of the Sulphur of Vitriol, or ev'n of common Sulphur, though the
Liquor appear'd clear enough, would immediately tinge a piece of new Coin,
or other clean Silver, sometimes with a Golden, sometimes with a deeper,
and more Reddish colour, according to the strength of the Solution, and the
quantity of it, that chanc'd to adhere to the Metall; which may take off
your wonder that the water of the hot Spring at _Bath_, abounding with
dissolv'd Substances of a very Sulphureous Nature, should for a while, as
it were gild, the new or clean pieces of Silver coyn, that are for a due
time immers'd in it. And to these may be added those formerly mention'd
Examples of the adventitious Colours of Mineral Bodies; which brings into
my mind, that, ev'n Vegetable Liquors, whether by degeneration, or by
altering the Texture of the Body that imbibes them, may stain other Bodies
with Colours differing enough, from their own, of which very good
Herbarists have afforded us a notable Example, by affirming that the Juice
of _Alcanna_ being green (in which state I could never here procure it)
do's yet Dye the Skin and Nails of a Lasting Red. But I see this Treatise
is like to prove too bulky without the addition of further Instances of
this Nature.

_EXPERIMENT XLIX._

Meeting the other day, _Pyrophilus_, in an _Italian_ book, that treats of
other matters, with a way of preparing what the Author calls a _Lacca_ of
Vegetables, by which the _Italians_ mean a kind of Extract fit for
Painting, like that rich _Lacca_ in English commonly call'd _Lake_, which
is imploy'd by Painters as a glorious Red. And finding the Experiment not
to be inconsiderable, and very defectively set down, it will not be amiss
to acquaint you with what some Tryals have inform'd us, in reference to
this Experiment, which both by our Italian Author, and by divers of his
Countrymen, is look'd upon as no trifling Secret.

Take then the root call'd in Latin _Curcuma_, and in English Turmerick,
(which I made use of, because it was then at hand, and is among Vegetables
fit for that purpose one of the most easiest to be had) and when it is
beaten, put what Quantity of it you please into fair Water, adding to every
pound of Water about a spoonfull or better of as strong a _Lixivium_ or
Solution of Potashes as you can well make, clarifying it by Filtration
before you put it to the Decocting water. Let these things boyl, or rather
simper over a soft Fire in a clean glaz'd Earthen Vessel, till you find by
the Immersion of a sheet of White Paper (or by some other way of Tryal)
that the Liquor is sufficiently impregnated with the Golden Tincture of the
Turmerick, then take the Decoction off the Fire, and Filter or Strain it
that it may be clean, and leisurely dropping into it a strong Solution of
Roch Allum, you shall find the Decoction as it were curdl'd, and the
tincted part of it either to emerge, to subside, or to swim up and down,
like little Yellow flakes; and if you pour this mixture into a Tunnel lin'd
with Cap Paper, the Liquor that Filtred formerly so Yellow, will now pass
clean thorow the Filtre, leaving its tincted, and as it were curdled parts
in the Filtre, upon which fair Water must be so often pour'd, till you have
Dulcifi'd the matter therein contain'd, the sign of which Dulcification is
(you know) when the Water that has pass'd through it, comes from it as
tasteless as it was pour'd on it. And if without Filtration you would
gather together the flakes of this Vegetable Lake, you must pour a great
Quantity of fair Water upon the Decoction after the affusion of the
Alluminous Solution, and you shall find the Liquor to grow clearer, and the
Lake to settle together at the bottom, or emerge to the top of the Water,
though sometimes having not pour'd out a sufficient Quantity of fair Water,
we have observ'd the Lake partly to subside, and partly to emerge, leaving
all the middle of the Liquor clear. But to make this Lake fit for use, it
must by repeated affusions of fresh Water, be Dulcifi'd from the adhering
Salts, as well as that separated by Filtration, and be spread and suffer'd
to dry leisurely upon pieces of Cloth, with Brown Paper, or Chalk, or
Bricks under them to imbibe the Moisture[25].

[Page 372]
_Annotation I._

Whereas it is presum'd that the Magistery of Vegetables obtain'd this way
consists but of the more Soluble and Coloured parts of the Plants that
afford it, I must take the liberty to Question the supposition. And for my
so doing, I shall give you this account.

According to the Notions (such as they were) that I had concerning Salts;
Allom, though to sense a Homogeneous Body, ought not to be reckon'd among
true Salts, but to be it self look'd upon as a kind of Magistery, in regard
that as Native Vitriol (for such I have had) contains both a Saline
substance and a Metall, whether Copper, or Iron, corroded by it, and
associated with it; so Allom which may be of so near a kin to Vitriol, that
in some places of _England_ (as we are assur'd by good Authority the same
stone will sometimes afford both) seems manifestly to contain a peculiar
kind of Acid Spirit, generated in the Bowels of the Earth, and some kind of
stony matter dissolv'd by it. And though in making our ordinary Allom, the
Workmen use the Ashes of a Sea Weed (vulgarly call'd Kelp) and Urine: yet
those that should know, inform us, that, here in _England_, there is
besides the factitious Allom, Allom made by Nature Without the help of
those Additaments. Now (_Pyrophilus_) when I consider'd this composition of
Allom, and that Alcalizate Salts are wont to Praecipitate what acid Salts
have dissolv'd, I could not but be prone to suspect that the Curdled
Matter, which is call'd the Magistery of Vegetables, may have in it no
inconsiderable proportion of a stony substance Praecipitated out of the
Allom by the _Lixivium_, wherein the Vegetable had been decocted, and to
shew you, that there is no necessity, that all the curdl'd substance must
belong to the Vegetable, I shall add, that I took a strong Solution of
Allom, and having Filtred it, by pouring in a convenient Quantity of a
strong Solution of Potashes, I presently, as I expected, turn'd the mixture
into a kind of white Curds, which being put to Filtre, the Paper retain'd a
stony _Calx_, copious enough, very White, and which seem'd to be of a
Mineral Nature, both by some other signes, and this, that little Bits of it
being put upon a live Coal, which was Gently Blown whilst they were on it,
they did neither melt nor fly away, and you may keep a Quantity of this
White substance for a good while, (nay for ought I can guess for a very
long one) in a red hot Crucible without losing or spoiling it; nor did hot
Water wherein I purposely kept another parcel of such _Calx_, seem to do
any more than wash away the looser adhering Salts from the stony substance,
which therefore seem'd unlikely to be separable by ablutions (though
reiterated) from the Praecipitated parts of the Vegetable, whose Lake is
intended. And to shew you, that there is likewise in Allom a Body, with
which the fix'd Salt of the Alcalizate Solution will concoagulate into a
Saline Substance differing from either of them, I shall add, that I have
taken pleasure to recover out of the slowly exhal'd Liquor, that pass'd
through the filtre, and left the foremention'd _Calx_ behind, a Body that
at least seem'd a Salt very pretty to look on, as being very White, and
consisting of an innumerable company of exceeding slender, and shining
Particles, which would in part easily melt at the flame of a Candle, and in
part flye away with some little noise. But of this substance, and its odd
Qualities more perhaps elsewhere; for now I shall only take notice to you,
that I have likewise with Urinous Salts, such as the Spirit of Sal
Armoniack, as well as with the Spirit of Urine it self, Nay, (if I much
mistake not) ev'n with Stale Urine undistil'd, easily Precipitated such a
White _Calx_ as I was formerly speaking of, out of a Limpid Solution of
Allom, so that there is need of Circumspection in judging of the Natures of
Liquors by Precipitations wherein Allom intervenes, else we may sometimes
mistakingly imagine that to be Precipitated out of a Liquor by Allom, which
is rather Precipitated out of Allom by the Liquor: And this puts me in mind
to tell you, that 'tis not unpleasant to behold how quickly the Solution of
Allom (or injected lumps of Allom) do's occasion the severing of the
colour'd parts of the Decoction from the Liquor that seem'd to have so
perfectly imbib'd them.

[25] _The Curious Reader that desires further Information concerning
Lakes, may Resort to the 7th Book of_ Neri's _Art of Glass, Englished (6
or 7 years since the Writing of this 49th Experiment) and Illustrated
with Learned Observations, by the Inquisitive and experienc'd Dr._
Charles Merret.

_Annot. II._

The above mention'd way of making Lakes we have tryed not only with
Turmerick, but also with Madder, which yielded us a Red Lake; and with Rue,
which afforded us an extract, of (almost if not altogether) the same Colour
with that of the leaves.

But in regard that 'tis Principally the Alcalizate Salt of the Pot-ashes,
which enables the water to Extract so powerfully the Tincture of the
Decocted Vegetables, I fear that our Author may be mistaken by supposing
that the Decoction will alwayes be of the very same Colour with the
Vegetable it is made off. For Lixiviate Salts, to which Pot-ashes eminently
belong, though by peircing and opening the Bodies of Vegetables, they
prepare and dispose them to part readily with their Tincture, yet some
Tinctures they do not only draw out, but likewise alter them, as may be
easily made appear by many of the Experiments already set down in this
Treatise, and though Allom being of an Acid Nature, its Solutions may in
some Cases destroy the Adventitious Colours produc'd by the Alcaly, and
restore the former: yet besides that Allom is not, as I have lately shown,
a meer Acid Salt, but a mixt Body, and besides, that its operations are
languid in comparison of the activity of Salts freed by Distillation, or by
Incineration and Dissolution, from the most of their Earthy parts, we have
seen already Examples, that in divers Cases an Acid Salt will not restore a
Vegetable substance to the Colour of which an Alcalizate one had depriv'd
it, but makes it assume a third very differing from both, as we formerly
told you, that if Syrrup of Violets were by an Alcaly turn'd Green, (which
Colour, as I have try'd, may be the same way produc'd in the Violet-leaves
themselves without any Relation to a Syrrup) an Acid Salt would not make it
Blew again, but Red. And though I have by this way of making Lakes, made
Magisteries (for such they seem to be) of Brazil, and as I remember of
Cochinele it self, and of other things, Red, Yellow or Green which Lakes
were enobled with a Rich Colour, and others had no bad one; yet in some the
colour of the Lake seem'd rather inferiour than otherwise to that of the
Plant, and in others it seem'd both very differing, and much worse; but
Writing this in a time and place where I cannot provide my self of Flowres
and other Vegetables to prosecute such Tryals in a competent variety of
Subjects, I am content not to be positive in delivering a judgment of this
way of Lakes, till Experience, or You, _Pyrophilus_, shall have afforded me
a fuller and more particular Information.

_Annotation III._

And on this occasion (_Pyrophilus_) I must here (having forgot to do it
sooner) advertise you once for all, that having written several of the
foregoing Experiments, not only in haste but at seasons of the year, and in
places wherein I could not furnish my self with such Instruments, and such
a variety of Materials, as the design of giving you an Introduction into
the History of Colours requir'd, it can scarce be otherwise but that divers
of the Experiments, that I have set down, may afford you some matter of new
Tryals, if you think fit to supply the deficiencies of some of them
(especially the freshly mention'd about Lakes, and those that concern
Emphatical Colours) which deficiencies for want of being befriended with
accommodations I could better discern than avoid.

_Annotation IV._

The use of Allom is very great as well as familiar in the Dyers Trade, and
I have not been ill pleas'd with the use I have been able to make of it in
preparing other pigments than those they imploy with Vegetable Juices. But
the Lucriferous practises of Dyers and other Tradesmen, I do, for Reasons
that you may know when you please, purposely forbear in this Essay, though
not strictly from pointing at, yet from making it a part of my present work
explicitly and circumstantially to deliver, especially since I now find
(though late and not without some Blushes at my prolixity) that what I
intended but for a short Essay, is already swell'd into almost a Volume.

_EXPERIMENT L._

Yet here, _Pyrophilus_, I must take leave to insert an Experiment, though
perhaps you'l think its coming in here an Intrusion, For I confess its more
proper place would have been among those Experiments, that were brought as
proofs and applications of our Notions concerning the differences of Salts;
but not having remembred to insert it in its fittest place, I had rather
take notice of it in this, than leave it quite unmention'd: partly because
it doth somewhat differ from the rest of our Experiments about Colours, in
the way whereby 'tis made; and partly because the grounds upon which I
devis'd it, may hint to you somewhat of the Method I use in Designing and
Varying Experiments about Colours, and upon this account I shall inform
you, not only What I did, but Why I did it.

I consider'd then that the work of the former Experiments was either to
change the Colour of a Body into another, or quite to destroy it, without
giving it a successor, but I had a mind to give you also a way, whereby to
turn a Body endued with one Colour into two Bodies, of Colours, as well as
consistencies, very distinct from each other, and that by the help of a
Body that had it self no Colour at all. In order to this, I remembred, that
finding the Acidity of Spirit of Vinegar to be wholly destroy'd by its
working upon _Minium_ (or calcin'd Lead) whereby the Saline particles of
the _Menstruum_ have their Taste and Nature quite alter'd, I had, among
other Conjectures I had built upon that change, rightly concluded, that the
Solution of Lead in Spirit of Vinegar would alter the Colour of the Juices
and Infusions of Several Plants, much after the like manner that I had
found Oyl of Tartar to do; and accordingly I was quickly satisfied upon
Tryal, that the Infusion of Rose-leaves would by a small quantity of this
Solution well mingl'd with it, be immediately turn'd into a somewhat sad
Green.

And further, I had often found, that Oyl of Vitriol, though a potently Acid
_Menstruum_, will yet Praecipitate many Bodies, both Mineral and others,
dissolv'd not onely in _Aqua fortis_ (as some Chymists have observ'd) but
particularly in Spirit of Vinegar, and I have further found, that the
_Calces_ or Powders Praecipitated by this Liquor were usually fair and
White.

Laying these things together, 'twas not difficult to conclude, that if upon
a good Tincture of Red Rose-leaves made with fair Water, I dropp'd a pretty
quantity of a strong and sweet Solution of _Minium_, the Liquor would be
turn'd into the like muddy Green Substance, as I have formerly intimated to
You, that Oyl of Tartar would reduce it to, and that if then I added a
convenient quantity of good Oyl of Vitriol, this last nam'd Liquor would
have two distinct operations upon the Mixture, the one, that it would
Praecipitate that resolv'd Lead in the form of a White Powder; the other,
that it would Clarifie the muddy Mixture, and both restore, and exceedingly
heighten the Redness of the Infusion of Roses, which was the most copious
Ingredient of the Green composition, and accordingly trying the Experiment
in a Wine glass sharp at the bottom (like an inverted Cone) that the
subsiding Powder might seem to take up the more room, and be the more
conspicuous, I found that when I had shaken the Green Mixture, that the
colour'd Liquor might be the more equally dispersed, a few drops of the
rectifi'd Oyl of Vitriol did presently turn the opacous Liquor into one
that was cleer and Red, almost like a Rubie, and threw down good store of a
Powder, which when 'twas settl'd, would have appear'd very White, if some
interspers'd Particles of the red Liquor had not a little Allay'd the
Purity, though not blemish'd the Beauty of the Colour. And to shew you,
_Pyrophilus_, that these Effects do not flow from the Oyl of Vitriol, as it
is such, but as it is a strongly Acid _Menstruum_, that has the property
both to Praecipitate Lead, as well as some other Concretes out of Spirit of
Vinegar, and to heighten the Colour of Red Rose-leaves, I add, that I have
done the same thing, though perhaps not quite so well with Spirit of Salt,
and that I could not do it with _Aqua-fortis_, because though that potent
_Menstruum_ does as well as the others heighthen the Redness of Roses, yet
it would not like them Precipitate Lead out of Spirit of Vinegar, but would
rather have dissolv'd it, if it had not found it dissolv'd already.

And as by this way we have produc'd a Red Liquor, and a White Precipitate
out of a Dirty Green magistery of Rose-leaves, so by the same Method, you
may produce a fair Yellow, and sometimes a Red Liquor, and the like
Precipitate, out of an Infusion of a curious Purple Colour. For you may
call to mind, that in the Annotation upon the 39th. Experiment I intimated
to you, that I had with a few drops of an Alcaly turn'd the Infusion of
Logg-wood into a lovely Purple. Now if instead of this Alcaly I substituted
a very Strong and well Filtrated Solution of _Minium_, made with Spirit of
Vinegar, and put about half as much of this Liquor as there was of the
Infusion of Logg-wood, (that the mixture might afford a pretty deal of
Precipitate,) the affusion of a convenient proportion of Spirit of Salt,
would (if the Liquors were well and nimbly stirr'd together) presently
strike down a Precipitate like that formerly mention'd, and turn the Liquor
that swam above it, for the most part into a lovely Yellow.

But for the advancing of this Experiment a little further, I consider'd,
that in case I first turn'd a spoonfull of the infusion of Logg-wood
Purple, by a convenient proportion of the Solution of _Minium_, the
Affusion of Spirit of Sal Armnoniack, would Precipitate the Corpuscles of
Lead conceal'd in the Solution of _Minium_, and yet not destroy the Purple
colour of the Liquor; whereupon I thus proceeded; I took about a spoonfull
of the _fresh_ Tincture of Logg-wood, (for I found that if it were _stale_
the Experiment would not alwayes succeed,) and having put to it a
convenient proportion of the Solution of _Minium_ to turn it into a deep
and almost opacous Purple, I then drop'd in as much Spirit of Sal
Armoniack, as I guess'd would Precipitate about half or more (but not all)
of the Lead, and immediately stirring the mixture well together, I mingled
the Precipitated parts with the others, so that they fell to the bottom,
partly in the form of a Powder, and partly in the form of a Curdled
Substance, that (by reason of the Predominancy of the Ting'd Corpuscles
over the White) retain'd as well as the Supernatant Liquor; a Blewish
Purple colour sufficiently Deep, and then instantly (but yet Warily,)
pouring on a pretty Quantity of Spirit of Salt, the matter first
Precipitated, was, by the above specified figure of the bottome of the
Glass preserv'd from being reach'd by the Spirituous Salt; which hastily
Precipitated upon it a new Bed (if I may so call it) of White Powder, being
the remaining Corpuscles of the Lead, that the Urinous Spirit had not
struck down: So that there appear'd in the Glass three distinct and very
differingly colour'd Substances; a Purple or Violet-colour'd Precipitate at
the bottom, a White and Carnation (sometimes a Variously colour'd)
Precipitate over That, and at the Top of all a Transparent Liquor of a
lovely Yellow, or Red.

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