Experiments and considerations touching colours first occasionally written, among some other essays to a friend, and now suffer'd to come abroad as the beginning of an experimental history of colours / by the Honourable Robert Boyle ...

EXPERIMENT XLVIII.

The third chief sort of the Adventitious Colours of Metals, is, that which is pro∣duc'd by associating them (especially when Calcin'd) with other fusible Bodies, and Principally Venice, and other fine Glass devoid of Colour.

I have formerly given you an Example, whereby it may appear, that a Metal may impart to Glass a Colour much differing from its own, when I told you, how with Silver, I had given Glass a lovely Golden Colour. And I shall now add, that I have Learn'd from one of the Chief Artificers that sells Painted Glass, that those of his Trade Colour it Yellow with a prepara∣tion of the Calx of Silver. Though having lately had occasion among other Tryals to mingle a few grains of Shell-silver (such as is imploy'd with the Pensil and Pen) with a convenient proportion of povvder'd Cry∣stal Glass, having kept them tvvo or three

hours in fusion, I was surpriz'd to find the Colliquated Mass to appear upon breaking the Crucible of a lovely Saphirine Blew, which made me suspect my Servant might have brought me a wrong Crucible, but he constantly affirm'd it to be the same where∣in the Silver was put, and considerable Cir∣cumstances countenanc'd his Assertion, so that till I have opportunity to make farther Tryal, I cannot but suspect, either that Silver which is not (which is not very probable) brought to a perfect Fusion and Colliqua∣tion with Glass, may impart to it other Co∣lours than when Neal'd upon it, or else (which is less unlikely) that though Silver Beaters usually chuse the finest Coyn they can get, as that which is most extensive un∣der the Hammer, yet the Silver-leaves of which this Shel-silver was made, might re∣tain so much Copper as to enable it to give the predominant Tincture to the Glass.

For, I must proceed to tell you (Pyro∣philus) as another instance of the Adventi∣tious Colours of Metals, that which is something strange, Namely, That though Copper Calcin'd per se affords but a Dark and basely Colour'd Calx, yet the Glas∣men do with it, as themselves inform me, Tinge their Glass green. And I remember, that when once we took some crude Cop∣per,

and by frequent Igintion quenching it in Water had reduc'd it to a Dark and Ill∣colour'd Powder, and afterwards kept it in Fusion in about a 100. times its weight of fine Glass, we had, though not a Green, yet a Blew colour'd Mass, which would per∣haps have been Green, if we had hit right upon the Proportion of the Materials, and the Degree of Fire, and the Time wherein it ought to be kept in Fusion, so plentifully does that Metal abound in a Venerial Tin∣cture, as Artists call it, and in so many wayes does it disclose that Richness. But though Copper do as we have said give somewhat near the like Colour to Glass, which it does to Aqua-fortis, yet it seems worth inquiry, whether those new Colours which Mineral Bodies disclose in melted Glass, proceed from the Coalition of the Corpuscles of the Mineral with the Parti∣cles of the Glass as such, or from the Action (excited or actuated by fire) of the Alca∣lizate Salt (which is a main Ingredient of Glass,) upon the Mineral Body, or from the concurrence of both these Causes, or else from any other. But to return to that which we were saying, we may observe that Putty made by calcining together a proportion of Tin and Lead, as it is it self a White Calx, so does it turn the Pitta di Crystalio (as the

Glassmen call the matter of the Purer sort of Glass, wherewith it is Colliquated into a White Mass, which if it be opacous e∣nough is employ'd, as we elsewhere declare, for White Amel. But of the Colours which the other Metals may be made 'to produce in Colourless Glass, and other Vitrifiable Bodies, that have native Colours of their own, I must leave you to inform you self upon Tryal, or at least must forbear to do it till another time, considering how many Annotations are to follow, upon what has in this and the two former Experiments been said already.

Annotation I.

When the Materials of Glass being mel∣ted with Calcin'd Tin, have compos'd a Mass Undiaphanous and White, this White Amel is as it were the Basis of all those fine Concretes that Goldsmiths and several Ar∣tificers imploy in the curious Art of Ena∣melling. For this White and Fusible sub∣stance will receive into it self, without spoy∣ling them, the Colours of divers other Mi∣neral substances, which like it will indure the fire.

Annotation II.

So that as by the present (XLVIII.) Ex∣periment it appears, that divers Minerals will impart to fusible Masses, Colours diffe∣ring from their own; so by the making and compounding of Amels, it may appear, that divers Bodies will both retain their Colour in the fire, and impart the same to some o∣thers wherewith they were vitrifi'd, and in such Tryals as that mention'd in the 17. Ex∣periment, where I told you, that ev'n in A∣mels a Blew and Yellow will compound a Green. 'Tis pretty to behold, not only that some Colours are of so fix'd a Nature, as to be capable of mixture without receiving a∣ny detriment by the fire, that do's so easily destroy or spoyl those of other Bodies; but Mineral Pigments may be mingled by fire little less regularly and successfully, than in ordinary Dyeing Fatts, the vulgar Colours are wont to be mingled by the help of Water.

Annotation III.

'Tis not only Metalline, but other Mine∣ral Bodies, that may be imploy'd, to give Tinctures unto Glass (and 'tis worth noting

how small a quantity of some Mineral sub∣stances, will Tinge a Comparatively vast proportion of Glass, and we have sometimes attempted to Colour Glass, ev'n with Pre∣tious Stones, and had cause to think the Ex∣periment not cast away. And 'tis known by them that have look'd into the Art of Glass; that the Artificers use to tinge their Glass Blew, with that Dark Mineral Zaffora, (some of my Tryals on which I elsewhere acquaint you) which some would have to be a Mineral Earth, others a Stone, and o∣thers neither the one, nor the other, but which is confessedly of a Dark, but not a Blew Colour, though it be not agreed of what particular Colour it is. 'Tis likewise though a familiar yet a remarkable practise among those that Deal in the making of Glass, to imploy (as some of themselves have inform'd me) what they call Man∣ganess, and some Authors call Magnesia (of which I make particular mention in ano∣ther Treatise) to exhibit in Glass not only other Colours than its own, (which is so like in Darkness or Blackishness to the Load-stone, that 'tis given by Mineralists, for one of the Reasons of its Latine Name) but Colours differing from one another. For though they use it, (which is somewhat strange) to Clarifye their Glass, and free

it from that Blewish Greenish Colour, which else it would too often be subject to, yet they also imploy it in certain proporti∣ons, to tinge their Glass both with a Red colour, and with a Purplish or Murry, and putting in a greater Quantity, they also make with it that deep obscure Glass which is wont to pass for Black, which agrees very well with, and may serve to confirm what we noted near the beginning of the 44th Experiment, of the seeming Black∣ness of those Bodies that are overcharg'd with the Corpuscles of such Colours, as Red, or Blevv, or Green, &c. And as by several Metals and other Minerals vve can give various Colours to Glass, so on the other side, by the differing Colours that Mineral Oars, or other Mineral Povvders being melted vvith. Glass disclose in it, a good Conjecture may be oftentimes made of the Metall or knovvn Mineral, that the Oar propos'd, either holds, or is most of kin to. And this easie vvay of examining Oars, may be in some cases of good use, and is not ill deliver'd by Glauber, to vvhom I shall at present refer you, for a more particular account of it: unless your Cu∣riosity command also vvhat I have observ'd about these matters; only I must here ad∣vertise you, that great circumspection is

requisite to keep this way from proving fallacious, upon the account of the variati∣ons of Colour that may be produc'd by the differing proportions that may be us'd betwixt the Oar and the Glass, by the Rich∣ness or Poorness of the Oar it self, by the Degree of Fire, and (especially) by the Length of Time, during which the matter is kept in fusion; as you will easily ga∣ther from what you will quickly meet with in the following Annotation upon this pre∣sent 48th Experiment.

Annotation IV.

There is another way and differing e∣nough from those already mention'd, by which Metalls may be brought to exhibit adventitious Colours: For by This, the Metall do's not so much impart a Colour to another Body, as receive a Colour from it, or rather both Bodies do by the new Texture resulting from their mistion produce a new Colour. I will not insist to this purpose upon the Examples afforded us by yellow Orpiment, and common Sea Salt, from which, sublim'd together, Chy∣mists unanimously affirm their White or Crystalline Arsenick to be made: But 'tis not unworthy our nothing, That though Yel∣low

Orpiment be acknowledg'd to be the Copiousest by far of the two Ingredients of Arsenick, yet this last nam'd Body being duely added to the highest Colour'd Metall Copper, when 'tis in fusion, gives it a white∣ness both within and without. Thus Lapis Calaminaris changes and improves the Co∣lour of Copper by turning it into Brass. And I have sometimes by the help of Zincle duely mix'd after a certain manner, given Copper one of the Richest Golden Colours that ever I have seen the Best true Gold En∣nobled with. But pray have a care that such Hints fall not into any hands that may mis-imploy them.

Annotation V.

Upon the Knowledge of the differing wayes of making Minerals and Metalls produce their adventitious Colours in Bo∣dies capable of Vitrification, depends the pretty Art of making what Chymists by a Barbarous Word are pleas'd to call Aman∣ses, that is counterfeit, or factitious Gemms, as Emeralds, Rubies, Saphires, Topazes, and the like. For in the making of these, though pure Sand or Calcin'd Crystal give the Body, yet 'tis for the most part some Metalline or Mineral Calx, mingled in a

smal proportion that gives the Colour. But though I have many years since taken delight, to divert my self with this pleasing Art, and have seen very pretty Productions of it, yet besides that I fear I have now for∣got most of the little Skill I had in it, this is no place to entertain you with what would rather take up an intire Discourse, than be comprehended in an Annotation; wherefore the few things which I shall here take notice of to you, are only what belong to the present Argument, Namely,

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 sub∣tile Powder, will of it self be brought by a due Decoction to give a cleer Mass Co∣lour'd like a German Amethyst. For though this glass of Lead, is look'd upon by them that know no better way of making Aman∣ses, as the grand Work of them all, yet which is an inconvenience that much ble∣mishes 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 Co∣lour 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 di∣vers 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 in∣troduce 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 Decocti∣on 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 adven∣titious 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 adven∣titious Colours of Metals, may not incon∣veniently 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 famous∣est Master in that Art, either in England or Holland, has confess'd to me, that neither o∣thers, 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 par∣ticular Metall. But of what I have known attempted in this kind, I must not as yet for fear of prejudi∣cing * 1.1 or displeasing others give you any particular Account.

The other way (Pyrophilus) of making Metals afford unobvious Colours, is by im∣buing divers Bodies with Solutions of them made in their proper Menstruum's, As (for

Instance) though Copper plentifully dis∣solv'd in Aqua fortis, will imbue several Bodies with the Colour of the Solution; Yet some other Metalls will not (as I else∣where 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 thought it ma∣nifest 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 Wa∣ter will not wash off, as it will ordinary Ink from the same parts. And divers o∣ther Bodies may the same way be Dy'd, some of a Black, and others of a Blackish Colour.

And as Metalline, so likewise Mineral Solutions may produce Colours differing enough from those of the Liquors them∣selves. I shall not fetch an Example of this, from what we daily see happen in the powdring of Beef, which by the Brine im∣ploy'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 deeline 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 Sul∣phur, though the Liquor appear'd clear enough, would immediately tinge a piece of new Coin, or other clean Silver, some∣times with a Golden, sometimes with a deeper, and more Reddish colour, accor∣ding 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 Bo∣dies; which brings into my mind, that, ev'n Vegetable Liquors, whether by dege∣neration, 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 ad∣dition of further Instances of this Na∣ture.

Notes

• * 1.1

  See the lat∣ter end of the fiftieth Experi∣ment.