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MONTHLY REVIEW

Published by the American Electroplaters Society

Publication and Editorial Office 3040 Diversey Ave., Chicago

VOL. XlV SEPTEMBER, 1927 No. 9


EDITORIAL

To the Officers and Delegates assembled at the 15th Annual Convention,

Greetings:
After reading the Financial and Membership Report of this office for the past year, a copy of which has been sent to all secretaries and also to each delegate, you perceive that the Supreme Society has had a fairly good year.

At the last convention it was ordered that the secretary find out what it would cost to furnish each branch with a copy of the “Proceedings of the next convention,” we have compared the cost of the last four conventions and find that if we deduct the average rate that has been charged us in the past from the bids received this year, we can furnish each branch (22 branches) with a copy 6? $3.50 per copy, and the Supreme Society at the same cost previously paid will receive 8 copies instead of 2 copies, and will be able to furnish each Executive Officer with a copy.

During the past year there were only three branches which made a call for constitutions, we believe every branch should see that a new member elected gets- a constitution and a membership card.

As regards membership cards, two branches did not take their 1927-1928 cards which means that the members of these branches do not have an official 1927-1928 card.

The Secretary recommends that each Branch get out a list of the names of the firms employing our members, so that these firms can be notified of our Annual Conventions from this office.

We also recommend that a committee be appointed to revise the Constitution and-have some printed, as our- supply is exhausted.

In reference to the Employment Bureau, we believe this work could be greatly improved by having proper forms printed so that both members and manufacturers-could state their requirements in detail, and the same would save a lot of unnecessary correspondence and time of the manufacturer and the - members, thereby making this service more efficient.

Respectfully Submitted,
Geo. Gehlmg, Secy.-Treas.


PAPER ON CHROMIUM PLATING

Presented by C. VanDerau

Annual Convention of American Electro-Platers’ Society Toledo, Ohio, June 30, 1927

 

Chromium Plating
In the last few years considerable attention has been given, by almost every manufacturer, to the problems and possibilities of commercial chromium plating.

The possibilities of chromium plating are of far reaching importance, entering into the fields of the following industries— ceramic printing, machine tool, oil, leather, soap, paper, plumbing, automotive, and all lines of rust resistant and ornamental finishing. A glimpse at the above field should stimulate the electroplater to greater activity in the development of chromium plating.

The present interest in chromium plating would lead one to believe that it is a new discovery, but chromium was deposited electrically as far back as 1854 by R. Bunsen. Continuation of this interest by the various industries, chemists, and electroplaters should change the status of chromium plating from an art to a science, thereby making it possible to chromium plate on as large a scale as that of nickel, silver, copper, and other plated metals.

The characteristics and properties of chromium as taken from the Chemical Rubber Company’s Hand book on Chemistry and Physics are as follows:

Specific gravity—6.92
Melting point—1305° Centigrade or 2741° Fahrenheit.
Boiling point—2200° Centigrade or 3992° Fahrenheit.
Specific Heat—.133 at 400° Centigrade.
Atomic Weight—52
Electro Positive Potential—.650

It is a very highly crystalline, brilliant silvery metal, very hard and brittle, and is not attacked by oxidizing acids such as nitric or sulphurous vapors. The above characteristics indicate the value of chromium for wearing, protective, and ornamental coatings. Chromium resists practically all acids with the exception of Hydrochloric acid, in which it is readily dissolved. This factor makes it possible for the electro-plater to salvage any defective chromium plate parts.

The idea of this paper is to give members of the American Electro-Platers’ Society the date gathered from the past year’s experience on chromium plated flood light reflectors and electrical appliances.
The following process has been worked out and is used on reflectors:—

(1) Clean in an alkali solution to remove soap and grease used in the spinning or drawing operation. Rinse in cold running water, and bright dip in a solution of sulphuric and nitric acids to remove scales from the surface of brass or copper material. Rinse in cold and hot water to remove acid.

(2) Polish reflectors on sub-felt, sewed muslin, or sheepskin wheels at a peripheral speed of 4000 to 5000 ft. per minute, wheels set up with two or more coats of glue and 160 Turkish emory to remove imperfections such as spinning marks, die marks, and material pits. ( Note: 180 Turkish emory cake and grease stick compounds used on polishing wheels.)

(3) Buff out polishing marks on loose or bias muslin buffs at a peripheral speed of 4000 to 6000 ft. per minute. (Note: Tripoli, silicate and lime buffing compounds used in buffing operation.)

(4) Color buffing of reflectors should be done on loose muslin or cotton flannel buffs running at a peripheral speed of 3000 to 4000 ft. per minute to remove buff stop and finger marks. (Note: Lime buffing compound used in this operation.)

(5) Rack and place in soap cleaner tank from 1 to 3 minutes to remove buffing compound, using cotton mop if necessary. Rinse in cold water. Immerse in sodium cyanide dip to remove alkali tarnish. Place in mild electro copper cleaner, not to exceed 1 minute at 6 volts. Rinse in cold water. Place in nickel bath from 5 to 15 minutes at a current density of 2 to 10 amperes per square ft. at 2 to 3 volts. Rinse in cold water, and change to a special chromium plating rack. Then place in chromium plating solution over an inverted lead anode from 1 to 10 minutes at a current density of 50 to 500 amperes per square ft. at 4- to 12 volts. Rinse thoroughly in cold running water. Before giving reflector the final rinse in clean hot water dry reflectors in sawdust to prevent excess water strains.

(6) Color buff chromium plated reflectors on loose muslin or cotton flannel buffs running at a peripheral speed of 3000 to 4000 ft. per minute to remove water strains and any irregularities of chromium deposit. (Note: Chrome green oxide in stick or liquid paste form is used as a buffing compound.)

Chrome oxide buffing compound can be bought from several plating supply houses Chrome oxide paste formula is as follows:

Denatured alcohol—50%.
Glycerine—5 to 10%.
Naptha—40 to 45%.
Dry chrome oxide—approximately 8 oz. to the gallon of the above solution.

This paste makes a splendid color buffing compound for producing a high, clear luster on bright chromium finishes.

(7) Inspect reflectors or any other parts under a screen of white tissue paper using a 150 watt lamp or bright daylight. Irregular plating will show up in this light, nickel appearing very yellow, as against a deep blue of chromium.

Several types of plating solutions have been used and data gathered over a period of several months. Solutions tested are as follows:

No. 1 Solution.
Commercial chromic acid—30 oz.
Water—1 gal.

This solution gave fair results, but required very high current densities, had very little throwing power, and was impractical for small parts.

No. 2 Solution.
Commercial chromic acid—28 oz.
Commercial chromic sulphate—1/2 oz.
Commercial boracic acid—1 oz.
Water—1 gal.

This solution had greater throwing power and gave a brighter and bluer finish. Boracic acid seems to be an important factor, as several times when chromic acid content was running low and throwing power was weak, an addition of 1 or lbs. of boracic acid to a hundred gallons of solution gave it new life and permitted working until the end of the day. Boracic acid apparently works about the same in chromium solutions as it does in nickel solutions, producing a finer grained deposit at the cathode.

No. 3 Solution.
Commercial chromic acid—60 oz.
Iron chromate—2 oz.
Water—1 gal.

Number 3 solution has given the best results. The addition of iron chromate has permitted the use of much lower current densities, thereby making it possible to chromium plate for any desired length of time; also making it possible to balance labor cycles. Parts have been plated for several hours in this solution with apparently no treeing action on the edges; also chromium has been plated over chromium without any tendency to peel. Reflectors that require 400 to 500 amperes in No. 1 and No. 2 solutions can be plated in this solution at 50 to 100 amperes. This comparison shows that No. 3 solution has much greater throwing power.

It is essential that chromic acid content in any of these solutions be above 20 oz. per gallon, although we have let chromic acid content drop as low as 12 oz. per gallon. At this point it was difficult to obtain a satisfactory chromium deposit. We are not in a position to state what we think is the high limit of chromic acid as we are obtaining satisfactory results at 60 oz. per gallon and believe that we can go higher in chromic acid content.

Chromic sulphate should not be added after the solution has been made as there is enough sulphate carried into the solution with the commercial chromic acid, as it contains about lo sulphate. During a six months’ test period, chromic acid content ranged between 40 and 60 oz. per gallon, while chromic sulphate ranged between .7 oz. and 2 oz. per gallon.

Chromic sulphate content in the three types of solution has shown the same tendencies to hold within the above limits. This leads us to believe that there is no necessity for extra additions of chromic sulphate to the plating solutions. Additions of chromic acid are governed entirely by the volume of work plated, all metal being taken from solution. Commercial chromic acid is approximately 50-51% metallic chromium.

We are not in a position to state what limits or additions of iron chromate are necessary, but believe that the content can go above 2 oz. per gallon without any serious results. Apparently the three most important factors in chromium plating solutions are chromic acid, chromic sulphate and iron contents.

It is absolutely necessary to determine additions to chromium solutions by analysis in order to get satisfactory results, although it may be possible to use a hydrometer to maintain the proper .solution densities. The following method of analysis is used.

Analysis of Chromium Plating Solutions
Dilute 25 cubic centimeters of the plating bath to 500 cubic centimeters and use portions of this diluted sample for the determinations to be made.

Sulphate—SO4
Place a 100 cubic centimeter sample in a 250 cubic centimeter beaker; add 8 to 10 cubic centimeters of concentrated hydrochloric acid (HCl) and 5 cubic centimeters of redistilled denatured alcohol; boil for one-half hour. This reduces the hexavalent chromium to trivalent and permits the precipitation of sulphate by barium chloride without contamination by barium chromate, which would occur to some extent even in hydrochloric acid if the chromium were not reduced. Make up to 150 cubic centimeters with hot water; bring to a boil, and add 10 cubic centimeters of 10% solution of barium chloride drop by drop, stirring the solution meanwhile. Allow the solution to boil a few minutes; then set the beaker on a hot plate where it will be at a temperature of about 60° Centigrade. Let stand 36 hours. Filter on a tight ashless filter paper; wash until free of chromium with a solution containing 10 cubic centimeters of 10% barium chloride and 10 cubic centimeters of hydrochloric acid per liter; then wash 5 times with a 1% by volume hydrochloric acid solution to remove the barium chloride (BaCl2) remaining in the paper. Ignite and weigh as barium sulphate (BaSO4). This weight x 82.3 equals SO4 in grams per liter of plating bath. This factor for barium sulphate (BaSO) to sulphate (SO4) is .41155. The sample is 1/200 of a liter of plating solution, therefore .41155 x 200 equals 82.3.

Chromic Acid—CrO3
Measure 10 cubic centimeters with a carefully calibrated pipette into a 600 cubic centimeter beaker; add 10 cubic centimeters of 50% sulphuric acid (H2SO4) solution and dilute to 500 cubic centimeters with cold water. Run in a solution of approximately 1/10 normal ferrous ammonium sulphate (40 grams plus 80 cubic centimeters of 50% sulphuric acid solution made up to 1 liter) from a burette until there is a slight excess. Use potassium ferri cyanide as an external indicator. Titrate the excess ferrous sulphate with 1/10 normal potassium permanganate solution. The deep green color of the reduced chromium makes the end point a little difficult to recognize, but after a few titrations the operator should have no difficulty. The clear green of the chromic ion changes to a violet shade at the end point; when this is reached one drop excess of the permanganate will give the solution a distinct purple cast.

The 1/10 normal value of the ferrous sulphate must be found each time chromic acid content is determined by titration against a 1/10 normal potassium permanganate solution.

Calculation of Chromic Acid (CrO3): The number of cubic centimeters of 1/10 normal ferrous sulphate used minus the number of cubic centimeters of 1/10 normal potassium permanganate used to come back equals the number of cubic centimeters of 1/10 normal chromic acid (CrO3) in the sample titrated; this multiplied by .00333 (equals grams or chromic acid per cubic centimeter of 1/10 normal solution) gives the weight of chromic acid (CrO3) in 10 cubic centimeters of the sample; and this weight multiplied by 2000 gives the chromic acid (CrO3) in grams per liter of the plating bath.

Trivalent Chromium—Cr+++
The size of the sample to be used depends on the amount of trivalent chromium present; this can be fairly well gauged by the color of the diluted sample; a clear yellow color indicates low trivalent chromium content—use 100 cubic centimeters of sample; a dark orange color shows a medium amount of trivalent chromium—use 50 cubic centimeter sample; while a dark red color shows high trivalent chromium content—use 20 cubic centimeter sample. The reason for limiting the size of the sample is that an amount of trivalent chromium weighing more than .040 grams when ignited to chromi trioxide (Cr2O3) is too bulky to be readily filtered when precipitated as chromium hydroxide (Cr(OH)3).

Dilute the sample to 100 cubic centimeters in a 250 cubic centimeter beaker; add 25 cubic centimeters of 50% by volume hydrochloric acid solution and 30 to 35 cubic centimeters of 50% ammonium hydroxide solution. Boil until the ammonium-chromic-hydroxide complex is broken up and all chromium is precipitated as chromium hydroxide Cr(OH)3. This requires one half hour boiling and the solution must be kept distinctly ammoniacal the whole time, adding a few cubic centimeters of 50% ammonium hydroxide as needed. Let the precipitate settle a few minutes and filter. Wash 2 or 3 times with a slightly ammoniacal solution of ammonium chloride (1% NH4Cl). It is practically impossible to wash this precipitate free of ammonium chromate so it is necessary to re-precipitate. Reject the filtrate and place the original beaker under the funnel and dissolve the chromium hydroxide (Cr(OH)3) on the paper by washing with 50 cubic centimeters of hot hydrochloric acid (1 volume of concentrated hydrochloric acid to 2 volumes of water). Wash paper with hot water or 1% hydrochloric acid till the volume in the beaker is 150 cubic centimeters; add 30 cubic centimeters of 50% ammonium hydroxide by volume; boil one-half hour as before; filter and wash; ignite and weigh. This weight will give R2O3—(that is Cr2O3 and any Fe2O that may be present). Subtract from the R2O the weight of FeO (as determined below) to get the weight of Cr2O3. The factor of Cr2O3 to chromium is .6842; if chromium is determined in a 100 cubic centimeter sample, which is equivalent to 1/200 of a liter of plating solution, then .6842 x 200 equals 136.8, the factor to convert trivalent chromium to grams per liter.

Iron—Fe.
To a 100 cubic centimeter sample add 60 cubic centimeters of bromine water (made by shaking a few cubic centimeters of bromine in a glass-stopped bottle with water), then add 15 cubic centimeters of sodium hydroxide solution ( 5 cubic centimeters having 1 gram of NaOH) boil hour. Trivalent chromium is oxidized to hexavalent and iron is precipitated. If the precipitate is black instead of red, copper, nickel, or manganese is present (generally copper), cool to about 50° Centigrade and filter; wash 2 or 3 times with dilute (1% NaOH) and dissolve the precipitate with hydrochloric acid ( 1 volume of acid to 2 volumes of water) as under trivalent chromium; wash. Make the solution ammoniacal; bring to boil; filter and wash. Ignite and weigh as FeO3. Copper has been eliminated by precipitation with ammonium hydroxide.

Copper—Cu.
If this determination is desired it is well to take a 200 cubic centimeter sample; reduce the chromium with hydrochloric acid and alcohol (10 cubic centimeters) as under the sulphate determination. Neutralize excess hydrochloric acid (HCI) with ammonia and then make the solution acid with hydrochloric acid so that there is 1 cubic centimeter of free acid per 100 cubic ce-ntimeters of solution, the volume of the solution should now be about 300 cubic centimeters. Pass in hydrogen sulphide for 1/2 hour; warm; transfer the sulphides from the paper into original beaker; dissolve in nitric acid and evaporate to fumes with 5 cubic centimeters of 50% sulphuric acid by volume; take up in water; note if any lead sulphate has appeared and filter if there is any. Weigh as PbSO4. Add 1 cubic centimeter of nitric acid to solution and determine copper by electrolysis. If electrolysis is not possible, the copper sulphide precipitate may be ignited and weighed as copper oxide (CuO). This, however, gives somewhat high results. The object of reducing with alcohol before passing in hydrogen sulphide is to escape the separation of a large amount of sulphur by reduction of chromic acid by hydrogen sulphide.

Temperatures of solutions must absolutely be controlled. A solution run between 115° Fahrenheit—130° Fahrenheit produces the best results on reflectors. When the temperature is below 110° Fahrenheit smutty and velvety deposits are obtained, in some cases having the appearance of being badly burnt, particularly at the edges. When the temperature of solutions is above 135° Fahrenheit they lose throwing power even though current densities remain the same. Deposits at high temperatures are very light and bright. This information was gathered by running solutions from room temperatures up to 180° Fahrenheit trying to find the workable limits.

Considerable thought should be given to facilities for current control. Three wire plating generators are more suitable for chromium plating, making it possible to use a double throw switch, giving a choice of either 6 or 12 volts depending upon the size of the article being plated.

Racking presents one of the big problems and the plater must forget the easy methods of wiring, hooking, and racking used in other lines of plating when he enters the field of chromium plating. Large pieces of work present less racking difficulties than smaller parts. On reflectors, lamp rings, radiator shells, etc., it is possible to use racks which clamp on either inside or outside of the rims making a contact on at least 75% of the circumference or perimeter, thereby having a tendency to uniformly distribute the current which gives more uniform deposits of chromium. When parts do not lend themselves to this kind of racking it is necessary to move the hook or wire to insure a chromium plate under the contact point. Racks should be made of copper buss bars or rods to facilitate the carrying of high current.

Many parts require special anodes and best results are obtained when the area of the anode surface is slightly less than the cathode surface. On relatively flat work this is not so important. Steel or lead may be used for anodes, lead being the most flexible for adjustment. Anode and cathode rods should be connected to buss lines with flexible cable so that the proper spacing between anode and object being plated can be obtained. Different shaped pieces require special adjustments between the anode and cathode.

Steel, crockery, or lead lined tanks can be used for chromium solutions. Lead coils should be used for steam and water, as iron pipe gives up in plating solution. Due to the excessive amount of fumes liberated by chromium solutions, it is absolutely necessary to provide ample hoods and ventilating facilities to protect the operators as the fumes attack the membranes of the nose and throat causing bleeding of the nose and excessive coughing.

In summing up the variables of chromium plating, it is necessary to recognize the fact that chromium plating is an engineering proposition requiring more definite methods and standardization than any other known form of electro-plating.

C. VANDERAU
Supervisor of Finishes, Westinghouse Elec. & Mfg. Co., Mansfield, Ohio.


THE PRODUCTION OF A RUST-PROOF ANTIQUE FLEMISH IRON FINISH UPON WROUGHT IRON, CAST IRON, MALLEABLE IRON, STEEL, OR IMITATION THEREOF UPON NON-FERROUS METALS

By Charles H. Proctor

Thirty or more years ago wrought iron was very much in vogue with its incidental Flemish Iron Antique Finish applied; the quiet beauty and richness of the finish, when correctly applied, is unsurpassed by any other finish applied to a metal surface.

History but repeats itself in the production of metal finishes; so today we find that wrought and flemish iron finish is much in vogue, metal goods in endless variety from chairs and benches to builders’ hardware, electric lighting fixtures and bric-a-brac being fashioned from wrought, and cat, and malleable iron in endless artistic designs.

Iron, steel, cast iron, and malleable iron are very susceptible to corrosion resulting in rust unless the surface of the articles finished in the Flemish iron finish is amply protected with suitable lacquers adapted to polished iron or steel surfaces. Even with this precautionary measure it has been found that when the finished product is carried in stock for any length of time especially near the seacoast or in damp or humid atmospheres—although amply protected with outer wrappings the surface of the finished iron products will rust. Many manufacturers have failed to realize that if after lacquering the surface of such products a thin coating of bees wax dissolved in pure turpentine, reduced to a paste, was further applied and wiped with soft cloths, they would have then produced a moisture-protected surface that would not rust, especially so if the first paper wrappings were impregnated with paraffin wax such as commonly sold under the commercial term of waxed papers.

One of the best fluid wax pastes that I have experimented with is known as “Johnson’s Floor Wax.” Articles made from sheet steel, such as the tops of electric ranges, and finished in brush nickel, when coated with this wax, have been immersed in water for months without rusting of the surface.

As a positive rust-proof factor for products made from gray iron steel and malleable iron, when finished in the Flemish iron finish, I developed for the manufacturer of fire-place heaters, hand irons, etc., a rustproof finish that in the author’s opinion will not rust when the articles are carried in stock or are in constant daily use, if a thin coating of fluid wax is applied at intervals to the surface of the finished product, as the housewife does to her furniture to maintain its luster and finish.

The methods in vogue for the production of Flemish Iron Finish depend to a great extent upon the basic metal surfaces. For cast and malleable iron surfaces, which have indentations and designs cast in them, all that is necessary is to soften up the surface of the iron by the usual iron pickles of hydrofluoric acid, if there is burnt-in sand in the surface of the iron, or hydrochloric acid if there is only a hard skin surface.

These pickles should be used hot; one part hydrofluoric acid and six parts water, headed to 140° F, makes an effective sand-removing acid pickle. Hydrochloric acid pickles are best prepared from equal proportions of acid and water, or one part acid to two parts water heated to 140° F. The heating of acid pickles makes them more active, therefore the time of the immersion of the metal articles in the acid pickles is considerably reduced, and more dilute pickles can be used to an advantage.

After pickling the iron articles should be thoroughly washed in water and then immersed in boiling water to which is added one ounce of tri sodium phosphate, soda ash, or aqua ammonia, per gallon of water.
The alkalis neutralize the acid in the pores of the metal and prevent rust during final manipulations.

After thoroughly drying, the surface of the iron may be roughed out, with 60 or 80 emery. The articles should then be immersed in a dead black air drying or baking japan, or air sprayed, and then dried according to the respective materials used. When the black finish so applied is hard and dry, the final polishing operation can be applied, which may vary from 120 to 180 emery finish.

The second polishing operation removes the black japan from the high lights, leaves it in the backgrounds and gives the antique or Flemish iron effect.

The surface of the iron should he thoroughly dusted from emery dust, preferably by air blast, to remove the polishing dust from indentations, then wiped with cloths moistened with benzine, benzole, or lacquer, thinner to remove grease, then lacquered as usual and finally wax-coated.

Some firms have adopted the method of nickel-plating the various iron articles; then, after polishing, they apply the antique black finish with black nickel solution, or iron and arsenic acid solutions, but such deposits do not prevent rust. Others apply pigment blacks and relieve the surface; as may be found desirable, the pigment blacks are either applied before or after the surfaces of the articles have been lacquered.

Black pigments that have no dissolving action upon the lacquers are best applied after lacquering; because of being of a semi-oily nature they can be readily removed with cloths moistened with a mixture of linseed oil and turpentine when the black is partly dry, without any reducing action upon the lacquer. All that is necessary is to see that the high lights are clean.

Articles made from bright cold-rolled steel which have the hammered indentations made mechanically, are best treated by the latter methods: Polish first; then lacquer; then apply the blacks and relieve as outlined.
It was, however, in order to eliminate the application of electro-deposited blacks as well as pigment blacks in the production of the wrought iron or Flemish iron finish that the author developed the new rust-proof finish, as applied to the sample cast iron book-rests I present to you for examination.

The method of procedure in the production of the finish is as follows:

The articles should be acid-pickled or sand-blasted and, if necessary, polished clown to the desired surface with usual emery polishing, then cleansed as usual, and then plated in cadmium solution.

The solution consists essentially of a cadmium mercury alloy, the mercury being alloyed with the anodes upon the basis of one to two per cent mercury with the metallic cadmium.

Water —One gallon
Sodium cyanide—96-98%, 7 ozs.
Cadmium oxide—3 ozs.
Caustic potash—2 ozs.
Black molasses—1 oz.

Anodes: 90% cadmium, 2% mercury; voltage 4 to 5; Amperage 10 to 25 per square foot of surface area; temperature of solution: 110° F.

It has been found advisable to use about 20% of the total anode surface required of sheet steel or durion, so as to avoid an excessive building-up of metal in solution.

The steel or durion anodes fill the gaps between the anodes and therefore produce a more equal distribution of the current and deposited metal without excessive metal reduction.

The upkeep of this type of cadmium solution is very low in cost, whether used as a basis for commercial cadmium deposits in the protection of steel products from rust and corrosion, or in the production of the rustproof Flemish iron finish referred to.

If the water line is maintained constant, an addition of one eighth of sodium cyanide and one thirty-second (1/32) ounces of caustic potash per gallon of solution per day will maintain it in constant operation. When barrel plating is used, the proportions of cyanide required may reach a maximum of one-half ounce per gallon with one-eighth of caustic potash.

These additions, however, can be best determined by current control; cadmium solutions should always be controlled by volt- and ampere-meters to produce standard results at the minimum cost of metal required and with a minimum of time. Create a standard and maintain it if you want uniform results.

Oxidizing Solution for Antique Flemish Iron Finish
After the iron or steel articles have been Cad-A-Loy plated as outlined, for a definite period of time to produce at least one to three ten-thousandth (1-3 10/1000) of thickness of Cad-A-Loy per square foot of surface area, which should be readily produced in ten to fifteen minutes’ time, if the maximum of current is used, wash the plated articles thoroughly in cold water, after cadmium-plating, then immerse direct in the oxidizing solution prepared as follows:

Water—1 gallon
Hydrochloric acid—5 ozs.
Platin-Nig—1/4 oz.

Temperature of solution, 120 to 140° F.; time of immersion of the Cad-A-Loy plated product, one to two seconds.

A deep black oxidized finish will result. The articles should be rewashed thoroughly in cold and boiling-hot water, they are then ready for the final finishing.

Finishing
The surface of the articles should now be scoured down with pumice stone mixed with water to a plastic mass. The scouring wheels may be either tampico, or made up from individual sections of buff cloth not more than six to eight inches in diameter; the speed of rotation should be kept down as low as possible, 500 to 600 R. P. M.

The oxidized black is quite soft, so does not require much friction or pressure to remove the excess from the high lights. After finishing as outlined, wash and dry out the articles as usual.

The articles are then ready for lacquering by either dipping or spraying. A good grade of brush brass lacquer, of any desired manufacture should be used. After the lacquer is hard and dry a very thin coat of wax should be applied as a further added finish and protection.

The finish thus produced will result in an ideal Flemish iron finish that will be rustproof and artistic and save the application of pigments or japans in the production of the antique black finish, so much admired in the Flemish iron finish.

I might mention in closing that Platin-Nig is the well known oxidizing agent at present so universally used in the production of antique and Dutch silver finishes, so much in vogue in commercial art.




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