A Treatise on Calico Printing, Of Grass-bleaching, or Fielding.

A Treatise on Calico Printing, VOL. I-II
Printed for C. O'Brien, Bookseller, Islington, and fold by Bew, Paternoster-row: Richardson, Royal Exchange: Murray, Fleet-Street: And the Booksellers of Manchester, Glasgow, Dublin, &c.
1792

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(35) Perhaps inhalation by the air may be mote proper, evaporation being more applicable to a chemical process.

(36) It is here offered as an opinion, that parks should be sloping from the middle.Having spoken of bran - bleaching or souring as subsequent to maddering, and observed (in a note) that by the improved mode of branning but a few pieces at a time, a white is almost procured without laying the pieces down (though that it need not be said is not proper to be done in all cases) it remains now to speak of laying cloth down to clear the ground or other parts, from the superfluous particles of colour; it is therefore observed that this effect appears to be chiefly accomplished by evaporation(35) and most effectually in sun-shine and moderately windy weather, she heat of the sun opening the pores and thereby giving egress to the colouring particles, detained in them till then; but in dull wintry weather, it is well known, the process of whitening goes on very slowly; there being no power by heat to dislodge those particles; for without it, watering is insufficient; the use of that operation being only to advantage when combined with the heat of the sun; one power infinuating itself into the pores of the cloth, and the other continually exhaling the watry particles, bringing away every time, some of the superfluous colour, and leaving those that by the action of the binding or contracting quality of the acids are with-held; though even these it is known, were the process carried on too long, would be removed in some degree; especially if the work consist of pale or tender colours.

It has been before said, that attention should he bestowed on the quality of the water, that it be light, soft, and free from filth; it likewise is necessary to attend to the quality of the soil of the field; for the facility and success of the operation depend on the mutual action of heat and watering,; therefore the drier the soil, or the more gravelly it is, the water will sooner pass through.it, and the heat on the surface will not be so much opposed as otherwise. (36) Smoke jar vapours from very foul boggy places, may be said to be injurious, if frequent, and in great quantities.

It is noticed, that cloth does not get white so soon in windy weather as in still sunshine; therefore, it appears that its influence penetrates the inward parts by its evaporating power, while wind only dries it, and in a manner prepares it; for succeeding operations of watering; for wind, alone, especially if cold, would close the pores of the cloth; but the power of heat naturally acts to the contrary; and in the case of evaporation, if seems the particles are partly dislodged by water, and then finally drawn out as those particles rise up.

In many places on the Continent, strange as it may seem; the printed goods are never watered, and to this dry bleaching it is owing that in most foreign printed goods, little colour is seen in the back, particularly in what is called Swiss chintz; but then the texture of the cloth is unavoidably nearly destroyed.

It is a particular circumstance to attend to in printing grounds, where printed goods are watered (which the writer thinks is every where the case in this country) that the water be not hard, nor tinged by any mineral quality; one reason for not watering, on the Continent, may be, the waters there abounding, with mineral imipregnations; indeed about London, work done in some places, is clearer in the white, from the superiority of the waters; and it is well known the soil in general in the north, from its mineral quality, is unpropitious to producing a good white, and without a good white no work can appear perfect.— See note 6.

(37) This may be considered philosophically as well as merely mechanically, the sensation of colours being caused by certain reflected coloured particles, or rays of light striking the eye, according as certain substances are disposed to receive those particles, thus, a bright colour lying by a dull one, the rays from each being intermixed with each other before they reach the sight, the bright colour helps to enliven the dull one, and the dull one deadens the bright one, so in painting, it is not suffieient that shadows be properly disposed, but that every colour, according to its quantity or proximity to another, communicates a portion to the parts near it, receiving at the same time, according to the laws of reflection and refraction, a portion likewise from the other.

(38) It is a pity this part is not better attended tot than it is in general, in preventing the ill-effects of high wind, as a little extra trouble would accomplish it, either by laying the work down in small parcels, or by means of moveable laths or ropes, or trees, hedge's, &c. placed as foreens.

(39) Thus, in all chemical operations, they are to be traced to the agency of the four simple elements; and, to come quite home, in producing fixtd colours on cloth; it is to be traced to the simple operation of an astringent.That a deal depends on the soil and water is further evident in the case of foreign articles, particularly some from India; for at a place called Seconge, the waters have, it is said, a surprizing tendency to whiten the cloth, (37) and of course to render the colours more brilliant, hence goods are brought thither from distant places for that purpose, as likewise to two or three other places on he same account.

In managing the field-work, the great concern is to put those kinds of work in the same parcels, that will take the same time to be brought white; that in fine open weather they are kept regularly watered, particularly work with delicate colour, and that the water be kept free from sedge and other filth; the other common processes of laying down,(38) pinning-, taking up-, drying, &c. every common fieldman is supposed to be acquainted, with, and therefore dwelling on those circumstances is deemed unnecessary.

Before this lection is closed, it is repeated, and begged it may be remembered, that in respect to particular processes, little is offered as positive, the difference of thinking and acting among diff erent practitioners rendering, such considence absurd (see note 16) but here it may be said, that the rejection or adoption of any mode of practice, is no further demonstrative of propriety than as it is, or is net, in consequence of a rational investigation of the object, therefore those who simplisy aay set of operations, (not from parsimonious views) but on the principle that nature universally observes in the sources of her operations, is alone likely to succeed, and (as particularly observed further on in respect to experimental colour makers) deserves credit even if he be un successful; for certain it is, that in all mechanical operations, as well as natural (however complex they may appear) there is a simple point, on which they all move, or from which they spring and branch out, and from this consideration the man of acuteness and reflection, whatever may be the subject of his employment, will trace every part through its connections and dependances to this first movement, this essential point, this actuating principle, and thence back again to its ultimate intended effects, endeavouring accordingly to remove what is superfluous, and supply what is deficient; while on the other hand, the man who proceeds in the vague uninformed manner, so often reprobated in this work, soon seeling his deficiency in this requisite, chain of knowledge endeavours to compensate for it, by repeated alterations of every kind, merely in the blind hope of accidentally stumbling on what is proper. (39)