The use of gold, when com­bined with good design, gives to cer­tain kinds of print­ing a dis­tinc­tion and qual­i­ty unob­tain­able by any oth­er means.

Update: August 2017 — Typore­tum’s tweet, below, shows the big dif­fer­ence between using gold ink and bronz­ing pow­der.

https://twitter.com/typoretum/status/785475011071148033

Gold print­ing is used in the pro­duc­tion of high-class labels, wrap­pers, box tops, cov­ers, greet­ing cards and oth­er work where bright, showy effects are appro­pri­ate.  Gold and oth­er metal­lic colours are pro­duced by the let­ter­press process in three dif­fer­ent ways –

• Metal­lic Ink: print­ing direct, using gold ink made from bronze pow­der, or sil­ver ink made from alu­mini­um pow­der or paste.
• Bronz­ing: print­ing first with a tacky prepa­ra­tion and imme­di­ate­ly dust­ing with bronze, alu­mini­um or oth­er metal­lic pow­der which adheres to the tacky prepa­ra­tion.
• Foil Print­ing: met­al foils are pressed on the paper or oth­er stock after the man­ner of block­ing. The foils are usu­al­ly sup­plied with an adhe­sive dress­ing which is made active by heat, so that heat as well as pres­sure is required to attach it to the paper or stock. Foils oth­er than met­al are avail­able and the process is lim­it­ed to plat­en and block­ing press­es

Gold Ink

The dif­fi­cul­ties asso­ci­at­ed with print­ing gold ink by the let­ter­press process and the rel­a­tive­ly poor results obtained on any oth­er than coat­ed or glazed stocks must be admit­ted. The ink is made from very fine bronze pow­der sus­pend­ed in a spe­cial oil var­nish vehi­cle, and it is not a homo­ge­neous com­pound. Some ink firms sup­ply the pow­der and vehi­cle sep­a­rate­ly for mix­ing in small quan­ti­ties fresh at the machine, with improved results. On cov­er paper, bonds and oth­er rough-fin­ish papers, it is advis­able to use a neu­tral size base for the first impres­sion and print the gold on the base. This helps to lift the gold ink from the plates. A sec­ond work­ing in the gold ink is also prac­tised and gives a brighter effect, but this is like­ly to be marred by feath­ered edges around the designs.

For best results, the rollers of the press must be in per­fect con­di­tion and set as only an expert can set them, with exact con­tact through­out. The impres­sion must be light and lev­el; exces­sive pres­sure moves the soft ink to the edges of the design. Mak­ing-ready should be accom­plished with some thin, light-coloured ink, and the gold ink mixed and run up fresh when the job is per­fect­ly ready for the run. In mix­ing the gold ink it should be kept thin so that it runs off the palette knife-nev­er short and but­tery-and only a small quan­ti­ty should be mixed at a time. When mak­ing two work­ings in the gold to get a brighter effect, the ink on the first work­ing should be kept sparse and the effect obtained on the sec­ond work­ing. Reg­is­ter must, of course, be per­fect. The machine must be washed up when­ev­er the quick dry­ing ink begins to thick­en on the rollers, or when the qual­i­ty of the work dete­ri­o­rates, which is usu­al­ly after a run of about two hours. It must also be washed up at the mid-day break.

The above remarks apply also to sil­ver ink, although this is not quite so dif­fi­cult to work and the results obtained are bet­ter. The ink, sup­plied ready mixed, is made from alu­mini­um pow­der, and com­par­a­tive­ly recent devel­op­ments in the meth­ods of man­u­fac­ture have great­ly improved the prod­uct.

Fre­quent­ly an addi­tion­al work­ing in gold or sil­ver is required in four-colour process work, and gen­er­al­ly speak­ing, with these light formes and good qual­i­ty coat­ed papers, metal­lic inks are ide­al for this pur­pose and have proved a great boon.

Bronzing

By far the greater bulk of let­ter­press work in gold is pro­duced by bronz­ing, and the results obtained by this method are excel­lent. The process involves, first, print­ing the sheet in a tacky medi­um such as bronze prepa­ra­tion and then dust­ing it with bronze pow­der which adheres to the prepa­ra­tion. It is then light­ly bur­nished to smooth and bright­en the bronze and the loose bronze is cleaned off the sheet. Small work can be bronzed by hand, but the work must be car­ried out under vac­u­um. Bronz­ing machines have been avail­able for a peri­od of years.

Home Office Reg­u­la­tions. All bronz­ing work is reg­u­lat­ed by Home Office Reg­u­la­tions, a copy of which may be obtained from H.M. Sta­tionery Office.

The Bronze Prepa­ra­tion. A brown pig­ment con­tain­ing copal var­nish and gold size is used as prepa­ra­tion, and is sup­plied in dif­fer­ent grades by all ink man­u­fac­tur­ers. When the design is print­ed and bronzed the prepa­ra­tion should dry hard on the sur­face of the paper by oxi­da­tion, and so hold and seal the bronze which is dust­ed on.

The dif­fi­cul­ties asso­ci­at­ed with the prepa­ra­tion are: pluck­ing; fail­ure to hold the bronze (which may remain mod­er­ate­ly loose on the paper and come off in han­dling); dry­ing on the machine.

Pluck­ing. The nature of the prepa­ra­tion to hold and seal the bronze on the paper must be strong and tacky. Noth­ing of a pen­e­trat­ing nature such as raw lin­seed oil or greasy sol­id sol­vents should be added if it can be avoid­ed. The best results are obtained by work­ing it as stiff as pos­si­ble, so that it is on the verge of pluck­ing all the time. Two grades of prepa­ra­tion should also be stocked, one stronger than the oth­er, so that either may be used alone or blend­ed to suit the require­ments of the par­tic­u­lar paper. Boiled lin­seed oil (which does not pen­e­trate) may be used spar­ing­ly as a reduc­er. The speed of the press should be reg­u­lat­ed to suit the paper, and pro­duc­tion must be con­tin­u­ous because the slight­est delay allows the prepa­ra­tion to begin set­ting on the machine and pluck­ing is inevitable.

Bronze not Hold­ing. This is one of the major prob­lems encoun­tered in bronze work. If the bronze rubs off, the appear­ance of the work is marred, and with food con­tain­ers (choco­late wrap­pers, etc.) the slight­est trace of loose bronze can­not be tol­er­at­ed. To pre­vent this the work is often over­print­ed with a very thin film of var­nish to seal the bronze.

The dif­fi­cul­ty aris­es chiefly in con­nec­tion with absorbent papers which allow the prepa­ra­tion to pen­e­trate so that insuf­fi­cient remains on the sur­face to hold the bronze.

The prepa­ra­tion should have the right char­ac­ter­is­tics so that it is large­ly a ques­tion of the quan­ti­ty car­ried, which should allow for the pen­e­tra­tion that takes place and yet leave suf­fi­cient on the sur­face of the paper to hold the bronze.

This is not easy, as designs will often include extremes of sol­id and fine detail and the sol­id areas will require so much prepa­ra­tion that the fine detail will fill in.

The work often takes the form of large sheets print­ed from elec­trotypes mount­ed on one large mount. Much can be done in the method and man­ner of the mak­ing-ready. The plates will need inter­lay­ing so that the sol­id parts are well up to type height, but the fine detail (as, for instance, long imprints in five-point lin­ing sans) is kept slight­ly below type height. The work on top (cylin­der) must also be care­ful­ly car­ried out, and all fine detail must fin­ish quite lev­el but light. In this way it will be found that much more prepa­ra­tion can be car­ried (with­out fill­ing-in) to hold and seal the bronze.

When the actu­al bronz­ing is tak­ing place some dis­tance away from the print­ing press, the sheets have to be car­ried in batch­es and there is the risk of the prepa­ra­tion part­ly dry­ing before the sheets are bronzed, the hold­ing pow­er of the prepa­ra­tion being large­ly lost. Notice should always be tak­en of the last sheet bronzed in each batch. This should be dust­ed clean occa­sion­al­ly to ensure that the prepa­ra­tion is not too dry to take the bronze. The num­ber of sheets car­ried in each batch can then be arranged accord­ing­ly.

Dry­ing on the Machine. Owing to its quick-dry­ing nature the prepa­ra­tion should not be runup on the machine until the job is ready to run, mak­ing-ready being accom­plished with a non-dry­ing ink. Dur­ing the run, the machine should not be allowed to stand, as even a stiort delay will allow the prepa­ra­tion to set. The machine will require wash­ing up at mid-day as well as at the end of the day’s run. As far as pos­si­ble no non-dry­ing sol­vents should be used in bronze prepa­ra­tion.

The Bronze Pow­der. Gold bronze pow­der is made from cop­per, brass and zinc alloy. The molten met­al is reduced in the process of man­u­fac­ture to minute leaf par­ti­cles and sift­ed through fine silk. It is then grad­ed in degrees of fine­ness by grav­i­ty, greased and pol­ished, but its flake-like form is retained. In addi­tion to the stan­dard tones (pale, rich pale, and rich), deep­er gold tones are pro­duced by the appli­ca­tion of heat. There are also cop­per-coloured bronzes (made from cop­per), sil­ver (made from alu­mini­um), and oth­er colours such as green, blue and fire-red, which are obtained by the use of dyes.

The finest tex­ture pow­ders have the best cov­er­ing pow­er, but are inclined to ​“pick up” on pre­vi­ous work­ings on the sheet and also stick to the paper-resist­ing dust­ing-if the paper is at all rough, as cov­er paper, etc..The coars­er bronzes will, there­fore, be found more suit­able for such con­di­tions. If coarse bronze ​“picks up” on pre­vi­ous work­ings on the sheet, the fault lies with the pre­vi­ous work­ings which have not dried cor­rect­ly. Great care in the choice and treat­ment of the ink is nec­es­sary when there is to be a sub­se­quent work­ing in bronze. How­ev­er, the trou­ble can be cured or min­i­mized by adul­ter­at­ing the bronze with mag­ne­sia pow­der, but in extreme cas­es the work will have to be treat­ed with mag­ne­sia alone before the bronz­ing oper­a­tion.

Hand Bronz­ing. Hand bronz­ing is used only for small sheets and com­par­a­tive­ly short runs on plat­en press­es. The work must be car­ried out under vac­u­um, and it is uneco­nom­i­cal to han­dle sheets larg­er than crown by the hand process. Up to this size, with prop­er arrange­ments, noth­ing excels the hand process for qual­i­ty.

A use­ful piece of equip­ment is the Vac­u­um Hand Bronz­er (Mark Smith patent), which com­pris­es a hand bronz­ing table of box-like con­struc­tion and a slop­ing glass front through which the work­er can watch his work. At the back is a vac­u­um box with a suc­tion fan dri­ven by a small built-in motor which also dri­ves a dust­ing-off device. For dust­ing-off pur­pos­es the sheets are pushed one at a time between two rollers through a long slot in the vac­u­um box and with­drawn against the action of the rollers which revolve inwards togeth­er and clean both sides of the sheet. The loose bronze is sucked away by the fan which also draws away all loose bronze dur­ing the process of hand bronz­ing. (See Fig. 1.)

A large pad of cot­ton wool, enough to fill the hand is used for the bronz­ing. The bronze is first light­ly dust­ed on, care being tak­en to avoid smear­ing the prepa­ra­tion, and then rubbed hard­er to bur­nish.; On rough-sur­faced papers the bronze must not be rubbed so hard that it becomes ingrained into the, paper around the design; if this occurs, it will be very dif­fi­cult (if not impos­si­ble) to dust off. The prepa­ra­tion grad­u­al­ly impreg­nates the sur­face of the cot­ton wool, which should be changed fre­quent­ly by pulling the wool apart; and turn­ing it about, oth­er­wise the pad will mark the work.

The sheets should be car­ried to the hand bronz­er in small quan­ti­ties that can be dealt with before the prepa­ra­tion becomes too dry to pick up the bronze prop­er­ly. Con­stant atten­tion must be giv­en to this.

When the bronzed work is dry, it can be cleaned of all loose bronze in the dust­ing rolls or oth­er­wise with cot­ton wool by hand under vac­u­um.

Machine Bronz­ing. When large quan­ti­ties of bronze work are han­dled the work will be print­ed in large sheets on cylin­der press­es and run through bronz­ing machines. The sheets can be car­ried from the one machine to the oth­er in dozens sup­port­ed on a card, placed on the flat feed-board of the bronz­ing machine, and hand fed. The speed of the two machines should be reg­u­lat­ed so that there is no delay.

Two main types of bronz­ing machine are avail­able* the cylin­der type and the more mod­ern end­less flat belt type.

Mark Smith Vac­u­um Bronz­ing Machine, There is still a good deal to be said in favour of the old cylin­dri­cal style of bronz­ing machine which gives long and reli­able ser­vice. A large drum cylin­der with tum­bler grip­pers and a flap (which clos­es the gap in the cylin­der and so pro­tects the lead­ing edge of the sheet) takes the sheet from the front lays, which swing away. As the sheet moves for­ward, it pass­es under the duct in which a plush-cov­ered roller revolves and flicks the bronze on to the sheet. Duct leads con­fine the bronze lat­er­al­ly to the lim­its of the design, and the turn of the duct roller is adjust­ed for length by a ratch­et and pawl arrange­ment to con­fine the bronze to the depth of the design. Ranged around the cylin­der are the var­i­ous dust­ing on, bur­nish­ing, and dust­ing off rollers and devices (thir­teen in all) cov­ered with plush and mon­key skin. The two bur­nish­ing rollers are of dif­fer­ent diam­e­ters and revolve at dif­fer­ent speeds, and also have a lat­er­al rec­i­p­ro­cat­ing motion. The last two dust­ing-off rollers make con­tact with the deliv­ery drum and so clean the back of the sheet. The bear­ings of all rollers are held in slots for instan­ta­neous adjust­ment: of con­tact.

The whole machine is effi­cient­ly boxed in, and there should be a win­dow for gen­er­al inspec­tion pur­pos­es. Sur­plus bronze drops to the bot­tom of the machine where it is drawn up by means of a suc­tion fan and con­veyed by a wide pipe back into the duct. The action of the fan exhausts the air inside the machine and cre­ates a par­tial vac­u­um so that air is con­tin­u­al­ly drawn into the machine from the room and takes any loose bronze with it. Over the duct the bronze drops down by grav­i­ty, and the con­duct­ing air escapes upwards along a pipe into the out­side atmos­phere. The machine is sim­ple to adjust and work, and every part is read­i­ly acces­si­ble.

Flat-bed Bronz­ing Machines. The lat­est type of bronz­ing machine is the flat-bed style. The sheets are led into the machines by an adjustable roller and are car­ried through on an end­less rub­ber blan­ket; there are nei­ther lays nor grip­pers.

In some of the machines the bronze is dust­ed on by oscil­lat­ing pads (“Mil­wau­kee,” ​“Fur­ni­val” and ​“Omega”) and in oth­ers by end­less plush bands work­ing across the machines (“Laco”). Pads are also employed to bur­nish and smooth the bronze on the design. There are lat­er­al dust­ing-off bands to remove the sur­plus bronze; these make con­tact with brush­es and in this way keep clean them­selves. The final dust­ing off is done by rollers which clean the sheet just before deliv­ery. All the rollers, pads and bands are adjustable.

The machines are ful­ly enclosed and are fit­ted with exhaust fans and air ducts. The strong inter­nal vac­u­um draws all sur­plus bronze away, and it is auto­mat­i­cal­ly fil­tered and gath­ered to be used over again when fresh­ened up with new bronze.

This type of machine is often described as ​“portable” because it is mount­ed on cas­tors and can be moved about the machine-room from one press to anoth­er. It is, how­ev­er, heavy and dif­fi­cult to move among the oth­er machines.

As all the oper­a­tions of bronz­ing, bur­nish­ing and dust­ing are done on the flat, these machines are of greater length than bronz­ing. machines of the cylin­der type and take up con­sid­er­ably more floor space.

Cou­pling the Bronz­ing Machine to the Print­ing Press. Some­times the bronz­ing machine is cou­pled up to the print­ing press so that the sheets run direct from one machine to the oth­er. Where the amount of bronze work war­rants this, it is an excel­lent arrange­ment. Apart from the sav­ing in time, which is con­sid­er­able, there is no delay between the print­ing and bronz­ing and the print­ed sheets are bronzed in the cor­rect sequence, with max­i­mum effi­cien­cy. Both styles of bronz­ing machine lend them­selves read­i­ly to the cou­pling sys­tem, the cylin­dri­cal style being cou­pled on and dri­ven by the print­ing press through a con­nect­ing shaft and mov­able clutch. This neces­si­tates a car­riage con­tain­ing trav­el­ling tapes dri­ven from the bronz­ing machine end (which can be sup­plied or made to spec­i­fi­ca­tion).

The two-rev­o­lu­tion press deliv­ery is suit­able for this prin­ci­ple, the sheets pass­ing from the tapes of the press to the tapes of the con­nect­ing car­riage and so to the bronz­ing machine, where a slop­ing tape feed is suf­fi­cient with­out oth­er attach­ment. When not in use the car­riage is pushed up out of the way and held by counter weight. This arrange­ment allows the print­ing press to run on oth­er than bronze work when required, and in the mean­time the bronz­ing machine may be used for dust­ing, etc.

In flat bronz­ing machines, the cou­pling arrange­ments are sim­pler and, as they have no grip­pers or lays, the need for exact tim­ing is not so nec­es­sary. The machines can be dri­ven inde­pen­dent­ly and the speeds syn­chro­nized.

Foil Printing

The use of foils in rolls has been devel­oped in con­nec­tion with book­bind­ing for block­ing the titles and designs on the fronts and spines of cov­ers for books, etc. These foils are usu­al­ly made on rolls 200 ft. in length, on a back­ing of glas­sine paper, and can be sup­plied in any width. They are pre­pared with an adhe­sive sur­face ready for block­ing on almost any mate­r­i­al, and the heat and pres­sure used in the press at the time of block­ing fix­es the foil to the mate­r­i­al. Foils are man­u­fac­tured in gen­uine gold (22 and 18 ct.), imi­ta­tion gold, sil­ver, a‑large range of metal­lic and flat colours and white. (V. Gould­ing and Co.
Ltd.)

The Machines. Var­i­ous machines are avail­able for using foil, rang­ing from small hand machines to large pow­er block­ers, incor­po­rat­ing roll feed attach­ments for the foil, and giv­ing impres­sions up to 25 per minute. Brass dies, brass type, or spe­cial elec­trotypes and stereo­types are fixed to the upper plat­en (or bed) of the press, which is heat­ed to 200F., and guides are fixed to the low­er plat­en (or draw­er) so that the cov­ers are set to a cen­tral posi­tion in line with the dies. Between the two platens is the foil, which runs off the roll in front of the machine and between two rollers at the rear so that a con­tin­u­ous strip of roll leaf runs across the face of the die. Under pres­sure the heat fus­es the adhe­sive so that the design in foil adheres to the stock and is pulled away from the back­ing paper. The scrap foil remains on the back­ing and is rewound at the back of the machine. At the same time a new sur­face of foil is pulled over the die ready for the next impres­sion. The roll feed attach­ment will draw any length of foil up to the full capac­i­ty of the heater plate. Oth­er types per­mit the draw­ing of two or more dif­fer­ent widths and lengths; this makes it pos­si­ble to cov­er dif­fer­ent sizes of impres­sion on the same die or dies, with min­i­mum waste of foil. Dif­fer­ent coloured foils can be used simul­ta­ne­ous­ly.

The advan­tages of foil print­ing for var­i­ous oth­er­wise dif­fi­cult sur­faces and mate­ri­als (as com­pared with the lift­ing and dry­ing of ordi­nary print­ing inks) are now real­ized, and the process and machines are used for print­ing on cel­lu­loid labels, radio pan­els and parts; met­al and plas­tic name­plates, dials and sci­en­tif­ic instru­ments, etc Dur­ing the war, foil print­ing was used wide­ly for the speedy pro­duc­tion of instruc­tion labels, name­plates, etc., for air­craft, tanks and ships, each of which requires num­bers of labels, either in met­al, plas­tic or trans­fer; of these, mil­lions were print­ed.

Foil Print­ing on Plat­en Press­es. Roll feed attach­ments and heat­ing plates are also suc­cess­ful­ly fit­ted to plat­en press­es of both the direct approach and clam-shell types, the attach­ment con­form­ing to the style of the par­tic­u­lar press, e.g. ​“Peer­less” roll feed attach­ment (see Fig. 2) is read­i­ly fit­ted to the heavy-duty ​“Crafts­man” or the ​“Vic­to­ria” press­es. The heater plate is also sup­plied com­plete with rheo­stat con­trol, reg­u­la­tion switch and clips for hold­ing the plates; the fit­ting of these attach­ments to equip the machines for foil print­ing in no way inter­feres with the ink­ing mech­a­nism of the press for ordi­nary work.

Foil Print­ing and Emboss­ing. When plat­en press­es are fit­ted with roll leaf feed attach­ments for foil print­ing, the prin­ci­ple also lends itself to the appli­ca­tion of foils and emboss­ing in one oper­a­tion for the pro­duc­tion of high-class cov­ers, show­cards, greet­ing cards, box tops, etc. The work is very effec­tive and dis­tinc­tive on any kind of stock. With dark cov­er stocks the opaque flat coloured foils are often an improve­ment on ordi­nary print­ing inks. The emboss­ing die is made ready in the usu­al way and forces made, and the con­tin­u­ous strips of foil are run over the heat­ed die so that the stock, foil and back­ing are all, embossed togeth­er, the foil being released from the back­ing to adhere to the stock. A fea­ture of the work is the’ per­fect reg­is­ter as the foil print­ing and emboss­ing are accom­plished in the same oper­a­tion.

His­tor­i­cal arti­cle from the British Print­er