Very detailed information on Overglazes

Very detailed information on Overglazes from Engelhard Hanovia. 1962

This is a historical document and none of the products mentioned are available from Hannovia, but are available from our suppliers.

We offer the information and suggestions in this booklet primarily to the new users of precious metal preparations, especially in the studio field of ceramic art. Elementary knowledge contained herein, we trust will lead to confidence and better results.

(ENGELHARD) HANOVIA

Bright Gold for Ceramic Decorating

Hanovia Bright Gold is actually fine gold dissolved in suitable organic vehicles.  When applied and fired on glazed ceramic the result is a brilliant mirror-like film of practically pure gold equal to a fineness of 22 karat. Liquid Gold is not as expensive as it might seem and therefore has universal appeal and added sales value. Because of its extensive covering capacity, bright gold decorations can be applied at a cost of only a few pennies.

Bright Gold is usually packaged in 100 gram bottles, although smaller bottles of 25 grams each can be obtained at a slightly higher cost. If kept sealed or corked tightly it will keep indefinitely.

Our Standard Liquid Bright Gold "N"  and Liquid Bright Platinum #40 is also available in 2 gram and 5 gram vials.

As manufacturers we have certain minimums. Small orders are referred to nearby distributors.

We offer several grades of bright gold and since the grade, or gold content, determines the selling price we prefer to quote prices by letter.

Applications

Before any application is made it is very important that the ware be PERFECTLY CLEAN AND DRY.

BRUSHING:

By far the most popular and versatile means of apply­ ing gold. It is important to have the right brush for the particular purpose. We advise using a good quality camel or sable hair brush. Ceramic suppliers carry a wide variety of brushes from a cut liner for applying delicate hair lines to the wide and flat type for covering large areas or com­ plete allover coatings. Brushes used for colors, etc. should not be used for gold unless very thoroughly cleaned. Traces of foreign materials left in a brush can affect the color and brilliance of the fired film.

To begin with, the brush should be well saturated and the excess forced from it. This permits an even deposit of gold with a minimum of repeat dippings. If the gold is worked from a jar or well, only a small quantity should be poured out at a time to prevent waste and undue exposure, which tends to thicken it.

Liquid bright gold should NOT be shaken. Since the gold is in solution any harmless sediment at the bottom of the bottle should best remain there.

Bright gold should be used as supplied. Thinning it will reduce its richness of color and will in extreme cases result in a purplish film due to lack of sufficient gold content; also too much thinner can cause the gold to flow and spread beyond control. If, due to exposure, the gold shows signs of tackiness and causes the brush to drag, a few drops of our Gold Essence #4 should be thoroughly mixed into the gold.

Banding and lining application requires a gold that will flow readily from the brush, and will leave a sharp, straight edge. For this type of work we recommend our Standard Liquid Bright Gold "N", which is our most popular gold for all-purpose application.

For design painting, which usually involves going over an already coated area more than once, we recommend our Liquid Bright Gold "Z", which is especially prepared to level out and remain open for a longer period of time. Other golds have a tendency to pile up with the result that they show streaking and possible dullness after firing.

Rippled or embossed surfaces (whether for complete coating or tracing work) present the problem of the gold running off the  high points and settling in the recesses. For a more even deposit, a gold with a higher viscosity is required.  Our Liquid Bright Gold "R"  is suited for this purpose.

For allover coating with Bright Gold, a thin, fluid type gold is preferred for ease of application, better coverage and high brilliancy.  For this work we recommend our "Regal Gold".

For glass, which has a lower firing range, a special gold, our #61-BB, is required. This type gold also lends itself for use on soft glaze pottery for low firing.

STAMPING:

Rubber stamping of bright gold is a simple method of applying designs singly, as border series or obtaining an allover effect. Individual designs can be obtained from local stamp suppliers, they should be made on a thin strip of hard rubber and mounted on a cushion of sponge or foam rubber and affixed to the customary wooden handle.

For production needs, stamping bright gold is offered ready for use, whereas for small scale operations our Liquid Bright Gold can be thickened to the proper stamp­ ing consistency. Left over liquid gold which has thickened is also suitable. Stamping Gold, which has a molasses-like consistency, should have a certain tackiness which causes a pull on the rubber stamp when applied.  If the gold is too liquid or thin, it will result in a purplish and squashy looking film. Should it become too thick or dry, a few drops of liquid bright gold mixed in well with a spatula or knife will restore the proper consistency. Since stamping deposits a much thinner film than banding, a slightly richer gold is necessary.

In applying stamping gold, it is spread on a glass slab or tile by means of a palette knife or rubber roller. The thinly spread gold is then picked up with the rubber stamp and transferred on to the ware. The spreading of the gold must be repeated every-so-often.

STIPPLING:

Stippling with bright gold is similar to stamping, as the same type of gold is used. It is also spread out in the same manner as for stamping, but picked up and transferred or daubed on to the ware by means of a sponge or steel wool. Beautiful effects can be obtained especially for feathering borders or adding high lights to figurines and artware. For very fine thread-like effects, lamb's wool is used.

RUBBER ROLLER:

The same thin spread-out layer of stamping gold can be picked up by a rubber roller and easily applied to edges of dinnerware, ash trays, or scalloped edge ware etc. Usually, this is quicker and more uniform than Initial attempts with a brush. The same application can enhance the high spots of ware which has a raised or embossed surf ace. Rubber rollers of medium hardness can be obtained from local photography supply stores.

SPRAYING:

The following information also applied to Hanovia Bright Gold and Platinum. Special preparations are offered for  spray application  in all materials.  Hanovia Lusters, whether sprayed by hand or with automatic equipment can produce unique and eye-appealing decorations of delicate transparent metallic tints. It is however important to observe certain elementary suggestions.  '

 

The ware must be perfectly clean and dry. Dust and dirt should be eliminated as much as possible to avoid imperfections in the fired film. It is advisable to shelter

the freshly applied lusters from falling or blowing dust. Where possible, the luster should be fired at once. Spraying adjacent to the lehr or kiln is advisable.

The compressed air used for spraying should be con­ trolled with a pressure regulating valve and gauge and must be free from entrained water.  A moisture filter should be installed between the spray gun connection and the main air line. The moisture filter should be checked periodically and "blown" now and then to remove any condensation. This simple precaution will also aid in re­ moving any oily residue in the line which could cause reticulated spots on the unfired luster.

To further minimize the chance of contamination, it is recommended that spraying nozzles and guns used for spraying lusters or other Hanovia metallic preparations be kept exclusively for this purpose. Guns used for ceramic color or other materials are almost impossible to clean thoroughly and the slightest trace of a foreign material may contaminate the preparations which may or may not be observed until after firing.

Since all the Hanovia spraying formulations have been prepared to make the operation as trouble-free as possible, no dilutions in the shop are necessary. The lusters should be used as you receive them. In addition, organic dyes have been added to aid the operator to see the application and make the coating more uniform.

It is recommended that when hand spraying the main airline or compressed air tank be equipped with a pressure regulating valve. Use a spray gun such as DeVilbiss No. PJGA/502/704/FX Spray Gun with a type PXB 519 Pressure Cup. Use a line pressure of 25-35 lbs. and a cup or atomizing pressure of about 10 to 20 lbs. The spreader adjusting valve can be adjusted to the fan spray desired.

With the ware revolving on a wheel, either hand or mechanically driven, the spray pattern is brought into the desired area. Using a slow, rhythmic motion, the material is applied until the entire area is coated with a luster pattern of equal density throughout. This is readily controllable by watching the luster spray build-up. When the . surface is completely "wet-out" or continuously smooth, the  decorator  should  terminate  the  application.  The depth of fired color is directly related to the strength of application.

The only other controllable factor is the distance from the nozzle tip to the surface of the ware. Generally, this is determined by the size and configuration of the ware it­ self. Slight experimentation by the operator will readily solve this problem.

Small artware objects and very limited  areas of decoration can be sprayed with an airbrush such as the Paasche airbrush or the Binks "Wren" airbrush.  Here, a line pressure of approximately 12 to 18 lbs. should be employed. Fine line decorations can then be achieved by adjusting the fluid control regulator.

Squeegee Gold for Screen Printing

Screen printing with Bright Gold has been mainly confined to the glass industry because of usual cylindrical shapes of bottles and glass tumblers.  However, the tile· decorators have recently discovered gold through screen printing and it has lent excitement and richness to decorative tile. Some shapes of dinnerware and artware also lend  themselves  to screen  printing.  We offer  special Squeegee Golds for screen printing on ceramics and for glass. The same type of gold can be spread out for the stipple application.

Most important is the screen. We recommend for gold the use of #230 Mesh Nitex or #306 Perlon. These fine materials are necessary to insure a thin but uniform print and to obtain the most economical use of gold. Screens used in printing ceramic colors are comparatively coarse and are not suitable for gold screening. The backing film on a gold screen must likewise be very thin. A heavy print not only costs more but sometimes :fires dull or blisters. A heavy coating of :film as the screen backing will also tend to produce a halo effect around the edge of each print.

Squeegee blades of 75 Durometer Rubber are suggested for flat screening. However, on surfaces of slight imperfections, a softer rubber squeegee is recommended. The edge of the squeegee blade must be sharp.

The Squeegee Gold is already prepared for use. The addition of a few drops of Imitation Oil of Lavender is sometimes recommended when screening for long periods

Squeegee Gold for Screen Printing

Screen printing with Bright Gold has been mainly confined to the glass industry because of usual cylindrical shapes of bottles and glass tumblers.  However, the tile· decorators have recently discovered gold through screen printing and it has lent excitement and richness to decorative tile. Some shapes of dinnerware and artware also lend  themselves  to screen  printing.  We offer  special Squeegee Golds for screen printing on ceramics and for glass. The same type of gold can be spread out for the stipple application.

Most important is the screen. We recommend for gold the use of #230 Mesh Nitex or #306 Perlon. These fine materials are necessary to insure a thin but uniform print and to obtain the most economical use of gold. Screens used in printing ceramic colors are comparatively coarse and are not suitable for gold screening. The backing film on a gold screen must likewise be very thin. A heavy print not only costs more but sometimes :fires dull or blisters. A heavy coating of film as the screen backing will also tend to produce a halo effect around the edge of each print.

Squeegee blades of 75 Durometer Rubber are suggested for flat screening. However, on surfaces of slight imperfections, a softer rubber squeegee is recommended. The edge of the squeegee blade must be sharp.

The Squeegee Gold is already prepared for use. The addition of a few drops of Imitation Oil of Lavender is sometimes recommended when screening for long periods or over a large area. This should be thoroughly mixed in with the gold only to loosen the gold and not for dilution. This should be avoided entirely except in the instance of a dry or hard screen gold.

The gold decorations on ceramics can be fired in the usual manner and temperature in the 1250° F-1350° F range.

A very rich two-tone gold effect can be obtained by first screening and firing a design print of matt ceramic color. The second print of bright gold is usually of a wide general area circle, oval or border. After the second fire, the  result is a matt or burnish type of gold pattern throughout a brilliant gold background. An embossed or relief effect is thus produced. Only a thin deposit of the color print is advisable.

Special Effects

For the artware and novelty decorators there exist unlimited possibilities for unusual finishes. We attempt to offer a few ideas which can be further expanded by interested parties.

Regal Gold. Essentially this is an imitation of the other­ wise expensive acid etched gold decoration. The effect is a design of dull gold which appears to be raised against a background of bright gold.

A special color is first rubber stamped on to the ware and after drying, a wide band of allover coating of bright

gold is applied over the design. A wide flat brush should be used and the gold should be easy flowing and on the thin side, so as not to disturb the underlying unfired color. We off er a special type regal gold, however our regular lining gold can also be used if thinned with a small amount of gold essence not in excess of 10%.

The colors used for regal work are of a special type and known as "Crown Derby Red", "Turkey Red" or "Imitation Gold Encrustation", and obtainable from various color houses. They are to be mixed per instructions furnished by the supplier, and the prepared color spread out and the design transferred by means of a rubber stamp just as in gold stamping work. It is important that only a very thin layer of color is deposited, since the gold will sink entirely into a heavy layer and fire out black. To obtain a thin and even color deposit, stamping through muslin or lawn is recommended.

The production appeal of this decoration is that it requires only one fire, although separate firings are occasionally preferred for reasons of control, particularly if overglaze colors or decals are also involved. In such instances, the gold fire should be lower than the color fire.

Crackled Gold. A unique vein or web effect can be achieved by means of Hanovia Marbleizing Liquid. A solid coating of bright gold is applied and after having dried to a tacky state, a coating of Marbleizing is brushed over it, which will cause the unfired gold to crackle. The degree of dryness of the gold coating is an important factor and the results depend mostly on the extent to which the gold has dried. In a semi-dry or tacky state, the marbleizing will produce large veins, whereas if the gold is completely or bone dry, the result will be a web-like effect. Initial experimenting at different stages of dryness will serve to give the decorator a good idea of the different effects obtainable which, as pointed out, range from wide prominent cracks to fine speckled or mesh finishes.

Marbleizing Liquid is a water-base preparation, it should be applied with a wide brush which should not be used for gold or luster work. In the event Marbleizing Liquid becomes too stiff for free and easy application, it can be conditioned with water.

There remains after firing a residue from the marbleizing which can be easily washed or wiped off with a damp cloth.

Bright Gold Over Color. Bright gold can be successfully used over fired overglaze colors, providing the proper firing technique is employed. It is important to fire the gold at least 100-200° Flower than the temperature used for the color. Over soft colors such as greens, it is often necessary to further lower the gold firing temperature. This is especially true over gloss enamels. If the gold is fired at the same temperature as the color, the tendency is for the thin metallic film to sink into the color and become dull and crazed. On the other hand, some unusual or antique effects can be obtained if the gold is deliberately over-fired.  Bright Gold applied over a glossy color will have a brilliant finish, whereas over a matt or semi-matt color, it will fire out dull.

Hanovia Ethyl Acetate Marble Effect. An overall application by brush or spray gun of Liquid Bright Gold, Platinum, Copper, Bronze or Luster Colors on pottery, glass, architectural ceramics and porcelain enamel, is the first step in this simple process. The application need not necessarily be perfect since it will be broken up. A light to medium application is sufficient. After the material has been applied it may be immediately broken up or at any time thereafter by means of spattering droplets of ethyl acetate on the gold, etc. An eye dropper, brush or any other means of spattering the ethyl acetate is suitable.

For specialized strata effects, a brush containing ethyl acetate can be daubed or streaked through the gold, etc. Some experimentation is necessary as various marbleized effects can be obtained by using a little imagination. The finished effect is especially striking when applied over a colored glaze, glass or enamel since it adds further dimension of color.

Very rich burnish-like effects can be obtained by application over a satin or matt glaze. A black or dark background provides a striking contrast for the metallic effects.

If the shape of the ware lends itself, rotation during the ethyl acetate spattering provides a better break-up pattern. Another suggestion is to apply the ethyl acetate to drip down vertical pieces which gives a long streaking effect.

By using two or more materials such as gold and copper applied over certain areas of a given piece, very unique combinations can be obtained.

The firing temperature is the same as in a normal gold decoration.

Weeping Gold Effect. This is a very striking, all over gold finish very suitable for artware. Raised islands of brilliant gold stand out from a background of dull but rich gold.

Only the highly vitrified type of ware may be used for this method because the porous nature of low fired bisque will absorb the gold coating and the effect is lost. The viscous glaze can be daubed on by brush in globs or even traced over the bisque in a design. If the glaze is applied too heavily, it may blister off in the firing. The firing of the glaze should be slow and even. Some are successful with a one-fire bisque and glost firing but most prefer to high fire the greenware first, for reasons of certainty. Commercially, the glaze gobs are applied by a special spatter spray gun.

The Liquid Bright Gold is applied all over the piece with a wide brush. The gold fire should be on the low side or around Cone 018-019 to prevent undue absorption into the bisque.

Satin Gold Drag. This decorative effect is a bit rough hewn and tweedy but very appealing. It can only be accomplished on a satin matt glaze. The background colors most complimentary to the gold are aqua, turquoise or pale blue and green.

A stiff or coarse bristled brush is required. It is also advisable to remove by scissors, in an irregular manner, a tuft of bristles here and there. The gold is thus smeared in jagged streaks over the satin glazed surface. Round pieces of ware are streaked by simply revolving them on a banding wheel and streaking on the gold by merely holding the brush against the surf ace.  Other shapes are streaked by smearing the brush casually but evenly.

The condition of the Liquid Bright Gold is very important. It must be on the thick side, enough to make the brush drag. Regular Liquid Bright Gold can be spread out on a tile or glass slab and allowed to evaporate to a thick­ er consistency, similar to molasses. If a thin or regular brushing gold is used, there is a possibility of a purplish halo or a starved gold appearance after firing. The thicker gold will not spread and with the semi-random streaking application, will fire out as natural strata of pure gold. We do offer a special gold for this method of application.

HANOVIA "MOTTLING" DECORATIONS

UNREADABLE… SORRY

Two Fire Combinations.  Truly unusual effects can be achieved by applying luster colors over a fired coating of Bright Gold or with a two color luster combination. Diluted lusters applied lightly allow the bright gold to glimmer through the transparent luster film in an un­ matchable beauty of color. There are many combinations possible, a few of them are listed herewith.

Ground Coat                    Top Coat                                     Result

Bright Gold    Luster #67-B      Mother of Pearl      Shimmering Iridescent gold of various hues.

Bright Gold      #44-B Carmine                                              Red Gold

Bright Gold      #127-A Turquoise   Blue, Green and Blue        Gold Sheen

Bright Gold      P 11030 Pink                                                                  Pink Gold

Bright Gold      19-F Light Orange   Brown                                     Reddish Bronze

Luster #44-B  Carmine #132 Dark Blue                                         Black

Luster #44-B  Carmine #127-A Turquoise  Blue                       Deep Violet
 Luster #296 Black   #189 Copper luster                                       Dark Indian Red

 

There are unlimited combinations such as applying marbleizing over a coating of gold or luster that has a fired undercoating of one or the other, which will result in the base coating showing through in veins or cracks.

Firing

Correct firing conditions are essential to good results. The proper temperature for the particular type of ware plus good kiln ventilation are of prime importance. Following is a list of recommended firing temperatures for bright gold, etc.

 

VITRIFIED CHINA                        Degrees F.                         Cone   (orton)

(Porcelain) ............................ 1375-1475                    016-014

EARTHENWARE

Amateur Artware.................., 1320-1360                 017-016

(Soft Glaze) .......................... 1200-1300                  019-018 !:1

PYREX GLASS ........................ 1200                             About 018

LIME GLASS ............................ 1100                           About 021

LEAD GLASS............................ 960-1000

These temperatures are general, there are instances where higher or lower :firings must be employed, depending on the hardness of the glaze. In principle the ware must be fired at a high enough temperature to obtain proper adherence; if under-fired, the decoration will wipe off, and if over-fired, sink into the glaze and lose its brilliancy.

In firing glass the temperature should be as high as the glass will stand without distorting, thus getting best adherence. Aside from the hardness of the glass and its composition, the shape and thickness of the pieces have also a determining influence on the :firing range, a squat heavy piece will withstand and require more heat than a tall and thin piece.

Ventilation

Temperature alone is not enough to insure good results with bright gold. Sufficient air is necessary to bring about complete burning out of the organic matter plus good ventilation to carry off the smoke and fumes that result in the firing.

In a small kiln just leaving the door ajar a few inches will permit enough air to enter to help the fumes escape. The door of the kiln should remain open until the smoking has ceased, which is at the approach of red heat or at a temperature of approximately 800° F. Poor ventilation is usually the cause of hazy or cloudy bright gold.

In large kilns it is advisable to provide for air inlets along the bottom. To complete the ventilating cycle an exhaust pipe may be installed at the top rear of the kiln. Under certain atmospheric conditions it might occasion­ ally be recommended to set up a slowly revolving fan to aid in the drawing out of the fumes. This could be used on days when the natural draft is poor.

 

Muffle kilns must be periodically checked for cracks, which should then be sealed to prevent gas from leaking into the interior.

The firing cycle of bright gold is very flexible; the resulting film will mature quickly if given adequate ventilation and proper temperature.  Under given conditions, gold can under actual production be fired within a one hour cycle with excellent results. In such a fast cycle, it will be necessary to raise the temperature to compensate for the loss of the soaking period which enters in slow firing. Other factors such as decals or colors actually dictate the firing cycle, inasmuch as both tend to blister if fired too rapidly.

Common Defects and Their Causes

Hazy or Dull Gold. As pointed out before, poor kiln ventilation and allowing fumes to settle on the decoration are principal shortcomings. In addition, foreign matter on the glaze, decal size, finger marks, dust, etc., will have detrimental effects. Moreover if the gold is exposed too long, it becomes dry and stiff, which will cause streaking, and in cases where applied too heavily, peeling. A few drops of our Gold Essence #4 properly mixed with the gold will restore its smooth workability.

 

Faded or Cracked Gold. Too high a fire, especially on soft glaze will cause the extremely thin gold film to sink into the glaze and result in a "burned away" appearance of the decoration. If for some reason a high fire must be maintained, a special "high-fire" bright gold should be employed.

 

Purplish or Poor Color. Thinning the gold too much will cut the metal strength to a point where not enough will be deposited.

 

Poor Adherence.  Under-firing along with poor ventilation is the principal reason for poor adherence. This is especially true with glassware where the tendency is to reduce the firing to avoid markings.

Breaking or Fuzzy Edges. When gold is applied over areas which have spots or traces of decal varnish, oil, grease or moisture, the result will be a bleeding and creeping effect. Clean ware is therefore of prime importance all around.

Contamination through colors, fluxes or other foreign matter, will severely affect the brilliancy of bright gold and may even render it unrecognizable in certain cases. Dirty brushes are frequently responsible for such troubles which usually remain undetected until after the firing.

Other Bright Metal Finishes

Besides bright gold, we offer a variety of other bright metal preparations, such as:-

Liquid Bright Platinum-which produces a brilliant white metal finish that will not tarnish and is also referred to as "Bright Silver".

Liquid Bright Palladium-which is similar to platinum and also a popular white metal decoration.

Liquid Bright Copper and Bright Bronze-which yield unique effects and are lower in cost than bright gold.

Liqui Bright Greengold-which produces a high yellow­ greenish metal effect. Greengold fires out with a slight haze which can be removed with a damp cloth.

The application and firing of these bright metal finishes is the same as for bright gold so that the recommendations pertaining to the latter apply to these materials as well. Our minimum for these specialties is 100 grams.

In addition to the bright metal preparations referred tom this booklet, we also offer the following materials:-

Burnish Gold-in liquid and paste form.

Burnish Gold-in "Pats" for the studio trade (Roman Gold).

Burnish Silver-in paste and liquid form. Requires burnishing and will tarnish.

Non-Burnish Matt Gold-gives the appearance of rich burnish gold when used for narrow bands or trim. Requires no burnishing.

Luster Colors--for china and glass.

Marbleizing Liquid-for crackling bright metals and lusters.

Gold Essence-for conditioning all bright metal preparations.           •

Luster Essence-for conditioning lusters.

Gold Erasers--for removing smears on fired decorations.

We offer detailed information sheets on all of our products and applications. These include special Metalo Organic Solutions for industrial, architectural, and electronic use. Inquiries  in these categories receive prompt replies.

Quality and Service

Hanovia precious metal preparations enjoy the high­ est reputation for quality and uniformity. Our products are the result of more than 50 years of specialized experi­ ence. They have proven their merits by being universally acknowledged and accepted. Our service is prompt.

All our materials are tested and fired before being shipped, therefore the Hanovia label is your guarantee of performance, which is important to anyone in the ceramic field who adds the highlighting beauty of precious metal to their product.