CHAPTER II.THE HELIOTYPE PROCESS.

A heliotype print is made in an Albion or other type-printing press, from a film or skin of bichromated gelatine, which, having been dried upon a plate glass (finely ground and waxed), is stripped off, then exposed to light in an ordinary printing-frame, under a reversed negative, then removed from the frame, laid face down upon a piece of black velvet, and the back of the skin exposed to light for a short time. The skin is next mounted upon a pewter plate, coated with a thin film of India-rubber, and placed upon the bed of the press, where the skin is covered with water from a sponge, and is allowed to soak for twenty or thirty minutes. It is then inked up, first with one roller, and then with another of a slightly different composition; the margin of the skin is then covered with a mask, with a suitable opening cut in it, then the paper that is to receive the image is put into position upon the mask. The picture is then printed.

The above is a rough outline of the process; now for the working details.

First of all, it will be necessary to understand that the gelatine skin from which the picture is printed must be of such a size as to allow a margin outside the actual picture of at least two inches all around, so that the rollers used in inking up will not overlap the margin, and strip the skin away from the pewter plate upon which it is mounted. For pictures 10 by 12, and under, a convenient size for the heliotype skin will be 21 inches by 15 inches, so the present chapter will treat entirely of skins 22 by 16, and the sizes of rollers, etc., given, as well as formulas for quantities of gelatine, etc., will be those most suitable for that size of skin; so if larger skins are adopted, the quantities here given must be modified accordingly.

The first consideration will be the apparatus and materials necessary. The first thing that commands attention is the press—an Albion or other typographic hand press—(the pressure necessary to print from a heliotype skin must be vertical, not scraping, therefore a lithographic press will not do). The press must have the bed fitted with several thicknesses of Kamptulican sufficient tonearlybring a sheet of thick zinc type high—“nearly” is said, because{153}due allowance must be made for the pewter plate (one-eighth of an inch in thickness) upon which the heliotype skin is mounted. Inside the tympan place a piece of good blanket, and also provide a loose blanket to lay over the paper when placed in position for receiving the impression.

The press must be fastened down to the floor, as plenty of pressure will be required in printing; a bench will be required close to the press, upon which either one large inking slab or two small ones can be placed, as well as the stock of printing papers, and a dish of water. A couple of good sponges are also required, as well as a supply of thick plate paper, to blot off the superfluous water.

THE ROLLERS.The quality of the print from a heliotype skin depends greatly upon having good rollers at hand for inking the image; therefore, the preparation of the rollers (two) must be made with every care. Get the usual printing office pattern, with handles in the centre. The stocks of these rollers are to be coated with India-rubber sponge, upon which is cast a mixture of gelatine, etc.

The quality of the print from a heliotype skin depends greatly upon having good rollers at hand for inking the image; therefore, the preparation of the rollers (two) must be made with every care. Get the usual printing office pattern, with handles in the centre. The stocks of these rollers are to be coated with India-rubber sponge, upon which is cast a mixture of gelatine, etc.

First of all, procure two 12-inch rollers with handles complete, and get the stocks coated with India-rubber sponge a quarter of an inch thick; then, with strong twine tie down about a quarter of an inch from each end, trimming off the edges outside the string, so as to make them nice and round; now place one of the stocks in position upon the base socket of a 15-inch seamless roller mould, then carefully smear the inside of the mould with a rag saturated with whale oil (taking care that the whole of the surface of the mould is smeared with the oil); now place the mould in position over the stock, put the loose socket in position at the top, when it is ready for receiving the composition for the inking roller, made as follows—

Scotch Glue1pound.Gelatine1pound.

Soak all night in sufficient cold water to cover it. In the morning squeeze out the superfluous water, and in a suitable size glue kettle, “Baine Marie,” or a jar placed in a pan of water, melt over a fire or Bunsen burner, then add 1 pound of green treacle, mix, and add 2 ounces of castor oil, 1 ounce of glycerine; stir well until all are thoroughly mixed, then pour into a warm jug, and from the jug pour into the mould as gently as possible; when the mould is full, take a piece of wood, and tap the outside of the mould all round, from bottom to top. That will cause any air bubbles that may be imprisoned in the mixture to rise{154}to the surface; then, if the mixture in setting should shrink, pour in more until the mould is quite full.

Now allow to stand for 12 or 18 hours, then remove the mould from the block, the socket from the top of the mould, then gently push the roller out. If due precautions have been taken, it ought to come out quite smooth. If it does not, the composition must be melted off in hot water, and the roller recast.

Composition for the clearing roller—Scotch glue, 1 pound; gelatine, 2 pounds; green treacle,1⁄2pound; castor oil, 2 ounces; glycerine, 1 ounce.

The glue and gelatine are soaked as before, then melted and mixed with the other ingredients. The stock (covered with India-rubber sponge) is placed inside the greased mould, and the roller cast exactly as before.

The rollers being pushed out of the mould, trim the ends square with the ends of the stock, then dip the ends of each roller in hot water placed in a saucer to a depth of half an inch, until the composition is slightly softened. In this condition the sharp edges are rounded off with a damp cloth wound round the fingers.

The object of thus rounding the edges is to prevent the roller marking the picture when rolling up the image.

These rollers are not fit for use directly after casting, but should be placed on the handles, and washed with turpentine on a slab, then allowed to hang for two or three days, and occasionally washed over with a rag dipped in alcohol.

When in use the inking roller should never be washed, but if the ink upon it requires cleaning off, it should be done by rolling it upon a clean piece of hard paper. When put away after a job, the roller should be coated with fatty ink. Clear it for work next time by rolling it on the paper.

The clearing roller will require keeping free from a superfluity of ink by washing.

Instead of making the roller composition, and casting rollers, some of the high class composition sold for type printing may be used, or the rollers may be obtained ready cast, which will, perhaps, be found far more economical in the long run.

PREPARATION AND CARE OF THE ROLLERS.Leather rollers when new should first of all be warmed in front of a brisk fire, and when warm rubbed with a piece of Russian tallow until the leather will not absorb any more. Then allow the roller to stand twelve hours{155}and repeat the operation; then take some middle varnish, smear some of it along the roller, and on a clean slab roll vigorously, and repeat the operation two or three times, scrape the roller with the grain, then roll up in varnish, allow to stand all night, scrape again, roll up again next day, scrape, then roll up with collotype ink, scrape and roll up, repeating this until the roller takes the ink evenly. After each time of using, scrape the roller before putting away, and if, after using, the roller is likely to be some time before being wanted again, after scraping smear it with Russian tallow, and wrap it up in paper, scraping it before rolling it up in the ink again.

Leather rollers when new should first of all be warmed in front of a brisk fire, and when warm rubbed with a piece of Russian tallow until the leather will not absorb any more. Then allow the roller to stand twelve hours{155}and repeat the operation; then take some middle varnish, smear some of it along the roller, and on a clean slab roll vigorously, and repeat the operation two or three times, scrape the roller with the grain, then roll up in varnish, allow to stand all night, scrape again, roll up again next day, scrape, then roll up with collotype ink, scrape and roll up, repeating this until the roller takes the ink evenly. After each time of using, scrape the roller before putting away, and if, after using, the roller is likely to be some time before being wanted again, after scraping smear it with Russian tallow, and wrap it up in paper, scraping it before rolling it up in the ink again.

Glue rollers should be hung up after use in a cold place, and before being put away should be coated with fatty ink, and just before using should be rolled clean upon a piece of rather fluffy paper; washing glue rollers in turpentine is not to be recommended, as it tends to harden them, and deprives them of their feeding quality. Glue rollers can be bought ready cast, and it is advisable to so buy them; any dealer in typographic material will supply them of a suitable quality, if the purpose for which they are required be stated at the time of ordering. The “durable” composition being very good for collographic printing, it may be purchased and used for the rollers, for printing from a heliotype skin, instead of the mixture given previously. For roller No. 2, add two ounces of gelatine previously soaked in cold water, and as much water squeezed out as is possible, then add this to the “durable” composition, and stir until the gelatine is melted and well incorporated with the composition.

These rollers may be cast upon the bare stock, without the India-rubber sponge, if preferred, but the India-rubber sponge makes the roller much lighter for use, which is a great consideration when long numbers are printed straight away.

These remarks are applicable to the rollers used in the work described in the previous chapters. Too much care cannot be given to the rollers. The skilled printer who has feeling for his work will soon learn to regard his rollers as the magic wands which produce his results. And well he may.

The ink used for heliotype printing is the best chalk ink as purchased in tins, brought to working consistency by mixing with lard, the two ingredients being well mulled on the slab. Varnish must not be used, lard being the best. Cocoanut and olive oil are also good.{156}

HELIOTYPE SKINis composed of a mixture of gelatine, glycerine, chrome alum, bichromate of potash, and water, dried upon a slab of thick plate glass. The surface of the plate glass must be very finely ground with emery powder (great care being taken that there are no scratches or holes, or they will spoil the skin), then thoroughly cleaned, and waxed with a solution of beeswax in benzole, a good plan being to first of all smear the glass with the wax, and then polish as much off as possible with an old linen duster (clean), then sprinkle with clean benzole, and with a fresh duster polish the plate thoroughly, noting well that wax marks will spoil the skin.

is composed of a mixture of gelatine, glycerine, chrome alum, bichromate of potash, and water, dried upon a slab of thick plate glass. The surface of the plate glass must be very finely ground with emery powder (great care being taken that there are no scratches or holes, or they will spoil the skin), then thoroughly cleaned, and waxed with a solution of beeswax in benzole, a good plan being to first of all smear the glass with the wax, and then polish as much off as possible with an old linen duster (clean), then sprinkle with clean benzole, and with a fresh duster polish the plate thoroughly, noting well that wax marks will spoil the skin.

This waxing need not be done every time a skin is made, but at intervals of every three or four skins.

The waxed glass requires levelling, so that the gelatinous mixture will set of an even thickness; therefore, a levelling stand must be provided, as well as a good and true spirit level.

The gelatinous mixture is dried in an oven (see Drying Oven in chapter on Collotype), at a temperature not exceeding 80° F., the time occupied being from thirty to forty hours.

THE PEWTER PLATE.The skin after exposure to light under the negative, etc., is mounted by means of a squeegee upon a plate of pewter 21 by 15 by1⁄8of an inch in thickness, and well polished. This plate is cleaned with benzole and coated with a solution of India-rubber in benzole (well filtered) and dried.

The skin after exposure to light under the negative, etc., is mounted by means of a squeegee upon a plate of pewter 21 by 15 by1⁄8of an inch in thickness, and well polished. This plate is cleaned with benzole and coated with a solution of India-rubber in benzole (well filtered) and dried.

THE MASK.To prevent the margin of paper upon which the ink picture is printed, being dirtied, it is necessary, after rolling up, to lay a mask over the skin, this mask having an opening in the centre the size of the picture. Paper suitable for this purpose is made by coating bank-post paper with a mixture of one part of gold size, and two parts boiled oil; this mixture is laid on the paper evenly with a sponge, then hung on a line to dry; when dry it is ready for use.

To prevent the margin of paper upon which the ink picture is printed, being dirtied, it is necessary, after rolling up, to lay a mask over the skin, this mask having an opening in the centre the size of the picture. Paper suitable for this purpose is made by coating bank-post paper with a mixture of one part of gold size, and two parts boiled oil; this mixture is laid on the paper evenly with a sponge, then hung on a line to dry; when dry it is ready for use.

THE HELIOTYPE SKIN.To prepare a skin 22 by 16, weigh out two ounces of a good gelatine, and soak it in ten ounces of cold water until soft, then place it in the porcelain{157}vessel of a “Bain Marie,” the outer vessel being duly provided with the requisite quantity of cold water; now place it over the fire or Bunsen burner, and stir until the gelatine is just melted, then add two drachms of glycerine; stir well, so as to mix thoroughly, and raise the temperature to 125° F.; add two ounces of solution No. 1, and two drachms of solution No. 2; stir well, then remove from the fire or Bunsen, and strain through muslin into a jug or beaker; now tie over the jug or beaker a clean piece of muslin, when the mixture is ready for pouring upon the ground side of thick plate glass, waxed, properly levelled, and slightly warmed. Begin by pouring in the centre of the plate, and gradually enlarge the circle until all the gelatinous mixture is out of the jug or beaker, then with a strip of clean card coax the gelatine to the edges.

To prepare a skin 22 by 16, weigh out two ounces of a good gelatine, and soak it in ten ounces of cold water until soft, then place it in the porcelain{157}vessel of a “Bain Marie,” the outer vessel being duly provided with the requisite quantity of cold water; now place it over the fire or Bunsen burner, and stir until the gelatine is just melted, then add two drachms of glycerine; stir well, so as to mix thoroughly, and raise the temperature to 125° F.; add two ounces of solution No. 1, and two drachms of solution No. 2; stir well, then remove from the fire or Bunsen, and strain through muslin into a jug or beaker; now tie over the jug or beaker a clean piece of muslin, when the mixture is ready for pouring upon the ground side of thick plate glass, waxed, properly levelled, and slightly warmed. Begin by pouring in the centre of the plate, and gradually enlarge the circle until all the gelatinous mixture is out of the jug or beaker, then with a strip of clean card coax the gelatine to the edges.

Now examine the film for air bubbles, which, if present, must be removed, either by pricking with a quill toothpick, or by coaxing to the edge with a piece of card.

As soon as the mixture has thoroughly set (which it soon does), remove it to the drying box.

Of course, the requisite quantity of gelatine for more than one skin may be melted at once, but it will be better only to strain into the pourer, from the “Bain Marie,” sufficient for one plate at a time, remembering that the quantity now given is for one plate only; therefore, if two, three, four, or more plates are to be dried at once, the quantities given above must be increased accordingly.

The stock solutions named above are compounded as follows:

No. 1.Bichromate of Potash1ounce.Water20ounces.No. 2.Chrome Alum1ounce.Water20ounces.

The temperature of the drying box must not exceed 80° F., and the time occupied will be from thirty to forty hours, during the whole of which time the temperature must be steadily maintained, but not exceeded.

When the skin is dry, with the point of a penknife separate the edges from the glass, and then lift the skin away, when it is ready for exposure to light under the negative. If it is desired to keep the skins a few days before using, they may be stored between sheets of dry brown paper in a drawer, or in a tin tube.{158}

It will be just as well to remark here that the dry heliotype skins are sensitive to light; therefore, the drying oven must be in a room illuminated by yellow light, or by artificial light, and the skins must not be exposed to daylight until they are in the printing frame.

PRINTING THE PICTURE.The heliotype skin is now ready for exposure under the negative, which is done in a printing frame 24 by 18 inches, provided with a plate glass front.

The heliotype skin is now ready for exposure under the negative, which is done in a printing frame 24 by 18 inches, provided with a plate glass front.

The negative must be reversed (i. e., instead of being taken direct in the usual way, a reversing mirror is used). The margin of the negative must be protected by a mask, with an opening cut the size and shape of the intended picture, the outside edges of the mask being sufficient to cover the rest of the skin.

To print, the back of the negative is cleaned, then laid with the film uppermost, in the centre of the plate glass front of the printing frame; the mask is then laid in position, the opening in the centre being adjusted so that exactly the amount of picture required will be printed upon the skin. The rest of the skin is protected from the action of light by the opaque margin of the mask. Now lay the skin, with the matt surface (i. e., the side that was in contact with the ground side of the glass plate during the process of drying) next the film of the negative; upon this lay a piece of dry black velvet, then a sheet of thick felt, then the back of the printing frame, fasten up, turn it over and see that the front of the glass is clean; then the frame is ready for exposure to light.

EXPOSURE TO LIGHTshould be made in a good diffused light, and its duration timed by means of an actinometer (see page107).

should be made in a good diffused light, and its duration timed by means of an actinometer (see page107).

As the time of exposure to light will vary according to the quality of the negative, no precise rule can be made, the best way being to get a small negative as near the same density as the other, cut off a piece of the skin, and placing it in a frame, expose to light at the same time as the big frame, and occasionally examine the progress of the small strip of skin in the dark room. A very good idea of the exposure of the big one can thus be had. A heliotype skin is properly printed as soon as the details in the half-tones show themselves. Of course, it should be understood that the small negative must be exposed to light at the same time and place as the big one.{159}

SUNNING THE BACK OF THE SKIN.The exposure to light under the negative being completed, remove the skin from the printing frame, and lay it with the side that has just been in contact with the film of the negative, upon a piece of black velvet, covering the margin of the skin outside the picture with strips of brown paper—these strips not quite touching the picture; now cut off a strip of the skin, say a quarter inch wide by one inch long, and double it lengthways, then cut a hole in a piece of brown paper and place the doubled piece of skin under it. Now remove the skin to diffused light, and as soon as the shape of the hole can be seen upon the undermost half of the small strip, the sunning of the skin has gone far enough, and it is ready for mounting upon the pewter plate.

The exposure to light under the negative being completed, remove the skin from the printing frame, and lay it with the side that has just been in contact with the film of the negative, upon a piece of black velvet, covering the margin of the skin outside the picture with strips of brown paper—these strips not quite touching the picture; now cut off a strip of the skin, say a quarter inch wide by one inch long, and double it lengthways, then cut a hole in a piece of brown paper and place the doubled piece of skin under it. Now remove the skin to diffused light, and as soon as the shape of the hole can be seen upon the undermost half of the small strip, the sunning of the skin has gone far enough, and it is ready for mounting upon the pewter plate.

The test here given for timing the sunning of the exposed skin is suitable, when a good ordinary negative has been used, but if a negative somewhat flat, or thin, has been used, then less sunning will be required, and if a very intense negative, the time of sunning must be increased, the object of the sunning being to reduce the relief caused by deep shadows.

MOUNTING ON THE PEWTER PLATE.The pewter plate upon which the exposed and sunned heliotype skin is mounted for printing from, must be well polished, free from scratches or other marks, the size being 21 by 15 by1⁄8of an inch in thickness. This plate is polished with a soft duster, then coated with a solution of India-rubber in benzole (about the consistency of sweet oil), the solution being poured on, and flowed to the corners and edges; then the plate is placed upon a levelling stand, and the India-rubber allowed to dry.

The pewter plate upon which the exposed and sunned heliotype skin is mounted for printing from, must be well polished, free from scratches or other marks, the size being 21 by 15 by1⁄8of an inch in thickness. This plate is polished with a soft duster, then coated with a solution of India-rubber in benzole (about the consistency of sweet oil), the solution being poured on, and flowed to the corners and edges; then the plate is placed upon a levelling stand, and the India-rubber allowed to dry.

This India-rubber solution is made by dissolving India-rubber solution, as sold in tins at any India-rubber warehouse, in benzole or benzoline.

When the solution is made it must be filtered through paper, or strained through five or six thicknesses of fine muslin, as the presence of any grit between the surface of the pewter and the skin would at once ruin the picture.

The India-rubber film being dry, place the pewter plate in a tray of clean water, the water being about a quarter of an inch deep; now trim the skin with a sharp pair of scissors to a little smaller than the pewter (201⁄2by 141⁄2), then lay the skin, face up, upon the surface of water, and at once lift the pewter plate from the water, keeping the skin in position by grasping the two top corners with the two forefingers. Now lay the pewter on the bench, and{160}with a nice, soft squeegee bring the skin into contact with the India-rubber film. This mounting must be done rapidly, as if the skin gets a chance of absorbing water it will frill, and be spoilt. The back merely requires moistening, and the squeegee, in expelling the water, brings it into contact with the India-rubber film. Now, with the squeegee, remove all the water from the plate, and then brush round the edges with some India-rubber solution, so as to reduce the chance of water, to be used subsequently, from getting under the skin.

PRINTING FROM THE SKIN.Now place the pewter on the bed of the press, and with a clean sponge cover the picture with clean, cold water, in sufficient quantity to form a pool about one-eighth of an inch deep, care being taken that the water does not extend as far as the edges of the skin.

Now place the pewter on the bed of the press, and with a clean sponge cover the picture with clean, cold water, in sufficient quantity to form a pool about one-eighth of an inch deep, care being taken that the water does not extend as far as the edges of the skin.

The water is allowed to remain on the skin for five minutes; it is then soaked up, and a fresh supply added, and this operation is repeated at intervals for twenty or thirty minutes, the object being to partly remove the bichromate, and also to allow the gelatine that has not been rendered insoluble by the action of light, to absorb sufficient water to enable it to repel the ink from the roller.

When it is judged that the image has been sufficiently soaked, with the sponge remove as much water as possible, then lay a clean sheet of paper upon the skin; upon the paper lay the loose blanket, lower the tympan, run the bed of the press under the platen, then pull over the lever, and subject to as much pressure as the press will give, allowing the pressure to “dwell” for a minute or two.

This is to “smash” down the highest relief in the skin, which, unless so smashed down, would interfere with the roller feeding the ink in the deepest shadows.

The skin is now ready for inking up with No. 1 roller, charged with the best litho. ink mixed with a little lard, just sufficient, and no more, to make the stiff ink distribute on the slab, the ink and the lard being thoroughly incorporated, either with a stiff palette knife or with a muller. The ink and lard being thus well mixed upon the slab, gather up the compound and place it in one corner of the slab.

For No. 2 roller take a portion of the above mixture and add to it a little more lard, and mix well, then place this in one corner of the other inking slab.

With the palette knife touch the roller No. 1 at short intervals with little dabs of the first ink, then roll it vigorously on the slab up and down, and then{161}across and sideways, until the ink is evenly distributed over the roller and the slab; now with the roller proceed to ink up the image. Use plenty of pressure, and turn the roller first one way, then the other, until the image shows itself vigorous and strong.

Now take No. 2 roller charged (in the same way as No. 1) with No. 2 ink well distributed (but do not use quite so much as with No. 1), and with a light pressure go over the inked image; this inking will fill up the light half-tones and clean up the image generally.

Before pulling an impression take a sheet of mask paper (which must be a little larger than the pewter plate), and in the centre cut a clean, sharp opening the size the picture must be. This mask, with the oiled side down, is adjusted in position on the skin; then turn back the edge furthest from the operator, and upon the extreme edge of the pewter place a few small dabs of stiff ink, return the margin of the mask over these dabs of ink, and rub down; these dabs of ink serve to keep the mask in position, when turned back for each inking up. If the margin of the mask paper projects over the pewter plate, and outside the bed of the press, it must be turned down, else it will tear when the bed of the press is run in.

The mask being laid in position to protect the margin of the print, lay a piece of matt enamel paper on the inked up and masked image, back this first with a sheet or two of clean blotting paper, then with a loose blanket; lower the tympan, and run the bed of the press under the platen and pull over the lever. The pressure requisite to pull an impression from a heliotype skin requires the full strength of an ordinary man to pull over the lever.

Now examine the print, and if it is flat and dirty, the skin has not been soaked sufficiently before inking up, so remove the ink left by the paper by washing it over with a rag soaked in turpentine, then wash with a wet sponge, blot off the surplus and with the sponge again put a pool of water over the image, and allow it to soak for about five minutes; again wipe it off with a sponge, smash down and ink up again.

If the image is black and white without half-tones, the fault may lie in the negative, which perhaps is too hard; or if that is all right, then the skin has not been sufficiently exposed in the printing frame, in which case it may be at once thrown away, as no amount of coaxing will make it yield a good print. Or it may be that the skin is too damp, in which case rub it gently with the water sponge, on which a few drops of alcohol have been sprinkled; then blot off, ink up again, and pull another proof.{162}

If the back of the skin is “sunned” too much, the print will suffer by being dirty and flat, and will require sponging over with a little of the ten per cent. mixture of ammonia in water; then blot off, and again ink up; take care and keep the ammonia sponges away from the other sponges.

If the deep shadows show a white margin and are difficult to ink up, the skin has been exposed under the negative for too long a time; and if “smashing” down does not remedy the defect, the only chance of saving it will be to allow the skin to get thoroughly dry, and then (say the next day) to soak it up again for an hour.

Spots on the margin of the print may be removed by carefully painting them over with a camel’s-hair brush charged with dilute cyanide of potassium, carefully washing afterward to prevent spreading.

Each time the image is inked up, the mask must be laid back, so as not to interfere with the roller; then after inking up, it is again laid in position, so as to protect the margin of the paper upon which the print is made.

It must be borne in mind that the first print from the skin will not be the best it is capable of giving, therefore, before any of the above-named dodges are resorted to, the image should be inked up and proofs pulled four or five times; as a generul rule perfection will not be attained until about ten or twelve prints are made, using each time a good paper, as a soft spongy one will not pick up the ink on the skin.

Of course, a plain black ink will not suit every class of subject, therefore, when the operator requires a different tint or color, it must be made by a judicious blending of stiff ink of the proper colors mixed with lard as given above. When a distinct change of color is required, it is not a good plan to wash No. 1 roller, but have a separate No. 1 roller for each color. No. 2 roller may be washed for such a purpose.

If it is desired to print two tints, the darkest tint is applied with the No. 1 roller, the lightest with the No. 2 roller.

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