Articles from Lapidary Digest

ELECTROFORMING (METAL PLATING) ON LAPIDARY

Written especially for Lapidary Digest by

George Butts (gtbutts@infinet.com)


Copyright 1998. This document may be copied and used in mineral and gem club newsletters without asking permission, given that the article is reprinted in toto and that cedit is given Lapidary Digest as the source. Others wishing to reprint the article may send a rquest to Lapidary Digest, using the e-mail form on the first page.

IMPORTANT NOTICE

I am not employed by, and have no commercial interest in, any vendor mentioned in this document. I have no formal training in occupational health or safety and all statements herein represent my personal understanding and practical experience. Anyone using chemicals or apparatus referenced in this document, do so at their own risk and liability.


ESSENTIAL APPARATUS

1. Source of DC current:

Features Required-
a) If it operates on standard household voltage, 117v AC, it's primary function is to:
1. Transform voltage down to safe level (below 50v).
2. Convert alternating current to direct current.
3. Filter to give a totally smooth DC current.
4. Shock hazard isolation (does not use a variable transformer with a common input/output line).
b) Current (Amperage) sufficient for largest intended plating area.
c) Current (Amperage) control from 10ma to machine max.
d) Current (Amperage) meter readable to 2 significant figures.
e) Protection from shorting of output leads and from overheating.
f) Two color coded leads to connect machine to the work.
Red = Positive...to anode
Black = Negative...to cathode (the work)

Useful-
a) Pilot light
Immaterial-
b) Voltmeter
c) Voltage control

2. Conductive Paint.
a) Rio Grande silver lacquer 335-068
alternate...none recommended

3. Plating NON-CYANIDE Solutions... aka "acidic" solutions.
a) Dalmar C1 Copper
alternate Rio Grande Electroform Copper 335-074
b) Dalmar C2 Nickel
alternate Rio Grande Electroform Nickel 335-078
c) Dalmar C3 Silver
alternate Rio Grande Electroform Silver 335-018
d) Dalmar C4 Gold 24k
alternate Rio Grande Electroform Gold-24k 335-054
alternate Rio Grande Electroform Gold-14k 335-053
24kt gold from Rio Grande is darker and rosier
compared to Dalmar. I prefer the brighter golden
yellow, others think dark is "richer"
e) Dalmar Acid Dip
alternate Rio Grande Acid Dip 335-075
f) Dalmar Electroclean
alternate Rio Grande Electroclean 335-076
g) Dalmar Copper Brightener B6
alternate Rio Grande Copper Brightener 335-065
h) Dalmar Nickel Brightener B7

Dalmar Mfg Co Rio Grande
941-275-6540 1-800-545-6566
http://dalmarplating.com http://riogrande.com
email- dalmar@peganet.com

4. Plating Anodes.
a) Copper
b) Nickel
c) Stainless Steel
d) Carbon

5. Jars, wire and miscellaneous.
a) Closable plastic or glass containers sized to immerse work
b) Uninsulated copper wire to suspend work (about 24ga).
c) bowls for rinsing and holding
d) simple calculator, measuring calipers
e) Midas Plating Guide (Rio Grande 550-289 $8.95)


BASIC PROCEDURE

1. Pre-test sample of proposed "rock" against decomposition in the plating bath.

2. Form "rock" into final "work".

3. Attach metallic circuit connector to the work. See discussion below on suggested attachment detail under "CONDUCTIVE PAINT AND 1/10 AMP PER SQ.IN."

5. Measure work and calculate plating in square inches.

4. Paint plate area with conductive paint.
Paint must present an electrically continuous circuit. Paint must include (at least) the tip of circuit wire. Paint must dry fully (9-18hrs).
Painted area should not be touched by bare hands after drying.

5. Copper Plate

a) Measure and Calculate work plating area.
Set current for 1/10 Amp per square inch.
simple perimeter example:
4.3"around x 0.12" wide = 0.52 sq.in. area required current = area/10 = 0.052 Amp (or 52 ma)

b) Connect red (+) rectifier lead to copper anode, then immerse anode into copper plating bath.

c) Connect black (-) lead to work, TURN ON CURRENT

d) Immerse work (cathode) into bath.

e) Time plating duration to desired thickness
(2hrs suggested).

6. Remove work, rinse well in tap water, acid dip, rinse, submerge and store in clean water until next plating.

Remove anode, rinse well, dry and place in storage.
Remove bath, wipe up drips, close tightly, store.
Copper Notes: expect bright, "fresh burnished" metal on all painted areas. Dull, rosy finish due to current too low. Dull, dark, loose or "powdery" finish from current rate too high. Air drying now can cause
desensitizing of surface (keep in wet storage).

Any ragged or sharp plating edges must be smoothed here. Use a very fine file, 600 grit SiC paper or the like.

7. Color Plate (Silver or Nickel+Gold)
general-
.open next bath, connect and insert next anode.
.pre-set current to proper value.
.remove work from water bath, touch off drips.
.attach black cathode lead to work.
.WITH CURRENT ON,immerse work.
.time plating process for desired thickness.

Silver notes:
Silver may be plated directly onto copper.
Silver plating requires stainless steel anode.
Reduce current to 1/8 current used for copper.
Plating time (suggested) is 10 min.

Gold notes (Gold must be plated over Nickel plating.)

Nickel plating requires nickel anode.
Current level for nickel is same as copper.
Plating time (suggested) is 30 min.

Gold plating requires stainless steel anode.
EXCEPT Rio 24kt which requires carbon anode.
Current level for gold is 1/2 current for copper.
Plating time (suggested is 5 min.).


CYANIDE, Sodium/Potassium salts

The process of metal electrodeposition requires a complex bath composition for a smooth, adherent plate. Cyanide is an inexpensive, excellent aid to this process for most of these metals and of wide general usage. Plating solutions with cyanide are sold side by side to those without. In some catalogs, this distinction is not clear. Dalmar Manufacturing currently says they have no "cyanides" in any of their solutions. Rio Grande is very clear as to which of their products contain cyanide. Rio Grande offers an MSDS sheet with a statement of hazard with each plating product, ask for it!

Cyanides are classed as a "violent poison" at 0.015 g/Kg lethal dose with intensely harmful effects at lower dosages (ingestion, inhalation, through broken skin). A solution with cyanide will release Hydrogen Cyanide gas, of "gas chamber fame", if mixed with an acidic solution. Cyanide antidote kits, hazardous in untrained hands, are available but require a prescription. Cyanides are a Federal Banned Hazardous Substance with substantial penalties to anyone who brings such into an inhabited dwelling and there is a very high safety liability to industrial shop managers. Cyanides MUST be disposed of by chemical degradation ONLY.

Good plating baths are now available which contain NO CYANIDE, are competitive in cost and, for lapidary electroforming, do an equally good job.

In summary: you MUST NOT USE electroplating solutions containing CYANIDE both by reason of inherent danger and Federal law within an inhabited dwelling or anywhere children or "uninformed adults have access".


GENERAL SAFETY AND GOOD LABORATORY PRACTICE

Follow the safety instructions from the supplier. It is known that some persons have an allergenic skin reaction from contact with certain metals. Gold and nickel salts are known to often be a problem. Some people develop such reactions by repeated contact (allergenic sensitizing). Most plating baths also have either a fairly acidic or alkaline pH.

Keep your body, especially eyes, out of contact. Don't bring food into the plating area. Wash your hands after plating. Keep solutions well marked in proper containers. Don't let anyone "fool around" with the solutions and apparatus, children or visitors especially. Watch out for spills into which a pet or child could step. Spills can result in dried metallic salt powder becoming airborne with bad consequences when inhaled.

Even though I don't heat the baths nor allow a current rate so high that "fizzing" from gas evolution happens, I made a plexiglas box (20"x20"x12") with doors as a chemical hood to contain the plating. I made this from $1/lb scrap plexiglass (scrap bin from Dayton Plastics). Any spills are easily wiped up. It's best NOT to work on a porous (wood) table that will absorb spilled chemicals.

You should wear protective attire, including gloves, an apron, and goggles. DO NOT use or store these products in a household, garage, or other area where children, uninformed adults, or pets may have access. All plating solution containers should be properly labeled. MSDS sheets should be available to all workers (posted).


GENERAL DISCUSSION

SOME ROCKS DECOMPOSE IN THE PLATING BATH(S)

Keep a half-ounce of the copper solution out in which to test the proposed rock (type). Drop a chip of a proposed rock into this and watch for gassing or fizzing like chalk in vinegar. After a half hour or so, remove the remains (if any), rinse, dry and examine. Some stones like Lapis just quietly and slowly disintegrate. Some discolor. A rock of complex composition might only "etch" in one zone or strata.


CONDUCTIVE PAINT AND 1/10 AMP PER SQ.IN.:

The non-conducting rock ("work") is painted with a substance which, when dried (or cured), conducts electricity. In the plating process, electricity is fed to the coating through a metal lead anchored to the rock. This lead may be part of the work, like a glued-on finding or jump ring, or may be held by adhesive to be cut free after the plating process is complete. Be sure there is an electrical path between the paint and bare metal lead. That is, watch out for adhesive on the metal- paint over that and onto the metal itself.

Metal plate "grows" from the paint so uniformly that any brush-stroke marks will be seen in the final surface. Coverage should be only enough that, if painted on a glass surface, would just be opaque. Thicker paint than that is wasteful and there is some indication that it results in a weaker plating job from thick paint cracking.

In reality, the paint film is poorly conductive. For this reason, it is necessary to "baby" the process along with a very gentle current flow as compared to standard electroplating. A "hint" in the Dalmar Mfg literature states that a current rate of 1/10 amp (100 ma) per square inch is required. I agree and I think of this as the "100%" rate. I find there is a current range around 100% where a tight, bright plate is obtained. Care needs to be taken to know the plating area and to pre-set the current flow accordingly.

The current formulations from Dalmar, especially 24kt Gold, have a wider window than Rio Grande but both work very well at the 100% current rate. Sometimes it's very hard to determine plating area, like a wrinkled or irregular surface, and the extra latitude is important.

If a copper wire is used as a conductor to suspend the work, like hooking through a glued-on finding, then the submerged wire section will also be plated. It is good practice to pre-paint the immersed wire with fingernail polish up to the contacting hook. This is because the metal conducts so well, relative to the paint, that it can drain current away into the solution, "shorting" current before it can be distributed into the paint. The symptom will be dullness at the paint extremity.

The paint, remaining forever under the plate, must adhere tightly or the metal overplate will loosen. The Rio Grande silver lacquer adheres to many surfaces quite acceptably but redissolves in strong solvents.

It is VERY important that the work be thoroughly cleaned. Watch out for diamond paste polishing with its silicone oil extender- especially tenacious! Silicone oil can be removed with methyl ethyl ketone or lacquer thinner. In the same vein, watch out for saw oil hiding in fissures or porous areas. The dried paint surface is very sensitive to being handled, easily becoming "desensitized" in dead areas where metal just doesn't plate. This is probably due to invisible substances from fingerprints. Thin cotton gloves, available from photographic supply stores for handling film, could be worn to eliminate a fingerprint problem.

Narrow plating on an inside curve (concave) may come loose, especially if the work surface there is highly polished. The only "fix" is to glue the plate back down with a non-brittle epoxy (Vigor CE451) or block elastomer (E-6000).


COPPER and NICKEL UNDER GOLD

Copper is always the first metal plated on the work. Copper is a pussycat in plating... it can be coaxed with ease onto many surfaces and most things plate onto copper but watch out for desensitizing of the fresh plate surface from oxidation. After copper plating and rinsing, dip in standard "acid", re-rinse, then store submerged under water while waiting for the next metal coat. Copper is cheap and strong so it makes sense to build the appropriate thickness with this substance before moving on to expensive metals.

Following copper, a case could be made that this is now simple plating, no longer "electroforming", but it seems that the current window is still very tight and careful "current driven" plating continues to be necessary.

Silver can be plated directly over copper. Gold also CAN be plated directly on copper but becomes irregularly discolored with a little aging of the piece. One opinion has it that copper "soaks" through the gold while another says that the gold plate is, in reality, somewhat permeable and copper tarnish products "sweat" into the overlaid gold metal matrix. Bottom line is that an isolating layer of Nickel is required.


CURRENT SOURCE, THE "RECTIFIER"

Electroforming is "current driven". Current is the rate of electrons flowing and measured as amperes ("amps"). Low current levels are often referenced as milliamps ("ma") where 1 milliamp is the same as 0.001 amp. The work is fed electrons at a constant rate predetermined according to the area to be plated: 1/10 Amp per square inch.

When we have a constant current regulator in the system, we are uninterested in the "voltage", the pressure driving the electrons. Without current regulation, voltage will need to be turned up and down to maintain a constant current level. This is something like working a water faucet to keep a fountain at a certain height while the neighbors are watering their lawns... it can be done but tedious over several hours.

A 3 amp system suffices for 30 square inches of plating area which seems to be plenty for most lapidary work. For example, to plate the bezel and finding of a baroque cab, there might be calculated a plating area of 0.65 square inches; thus, needing a current of 0.65/10 amps or 0.065 amps (65ma). On the other hand, the back side of a desk-displayed geode might measure 25 sq.in., needing 2.5 amps.

An automobile battery or a moderate sized gel-cell would be adequate as a current source but must be recharged after use and stored under a trickle charge. Radio Shack sells a 3A DC supply (22-504) for $39.95, regulated to present 13.8v to the output and protected for shorting or overheating. RS also has digital meters from about $50 capable of the needed measurement range of 10ma up to 3 amps. For technical types, a constant current regulator which plugs into the circuit between the source and the work (in the positive lead) can be easily and cheaply made from a few common electronic parts. Mounting the parts in a case with an adequate heat sink and so forth is not so easy without a work shop and a bit of technical knowledge. Commercial units tend to be quite pricey for electroforming use.


METAL REMOVAL; ROCK RECOVERY

If a problem happens that the metal needs to be removed, remember the weak boundary layer of conductive paint. The metal deposits on and into the paint surface but not completely to the base rock. For Rio Grande solvent based silver lacquer, immerse for a time in lacquer thinner (not paint thinner) and the metal edges will become loosened and can be plucked at. The metal plates as a "full hard" substance, meaning it is rigid and doesn't peel away very well but it can be freed with persistence.


HEAT & AGITATION

Unlike standard plating, electroforming solutions are formulated to be used at nominal room temperature. Yes, for optimum results, it is a good idea to rotate the work slowly or periodically during the plating interval. This is difficult to set up, especially with a "tree" of multiple objects being plated simultaneously (when it might be most needed). Be aware that bath geometry can make a difference and the part(s) facing the anode can get more metal than the "backside".


BRIGHTNESS, BRIGHTENERS & PROPRIETARY ADDITIVES

Plating baths are complex and literature references are made to "brighteners", a host of disparate chemicals, mostly organic, having no "logical" reason to be in the formulation. It is known that, for a given bath, small amounts of these select chemicals assist in enabling metal atoms to deposit as a smooth "prairie" rather than in dulling "hills". Brighteners seem to deplete before all the metal is plated out of a solution and the usable current window tightens to an impractical level. Electroform solution manufacturers sell their brighteners. If a good plating solution goes bad too early, suspect the need for brightener. Follow the suppliers instructions. Only a small amount should be needed and too much can be as bad as too little. Wow, is this witchcraft or what? Don't use brightener from one supplier in the solution from another. Don't mix baths like copper brightener in a nickel bath unless specified by the manufacturer.


MASKING

It is said that, for rocks which are sensitive to the plating baths, the work can be dipped in a thin solution of masking agent which dries to an invisible but protective film. Conductive paint may then be applied and the process continued as usual. I have had some success with SCJohnson's "Future" floor wax, a solution of ammonia-soluble acrylic polymer. It seems to be hardened and toughened by the solutions, yet easily removed with a wash of ammonia.

To make an unplated design in the metal, I have had good luck drawing on the dried paint with a Sanford Ultra Fine Sharpie (permanent) marker. After plating, it's a bit of a problem to clean off the mark (and paint underneath) without disturbing the adjacent metal but, otherwise, works pretty well.


CHECKING THE CURRENT WINDOW (TESTING)

When the plating process goes awry, tests are needed. The idea is to plate one side (only) of something to which the paint adheres fairly well and send it through the process to check what's happening. I use waterproof laboratory paper but smooth masking tape folded over on itself will also work. Cut a strip of material 5"x1/2". Mark the backside in 1/2" sections and paint the face with conductive paint.

When dry, 1/2" sections may be cut off to test copper plating at various current levels around the 100% (25ma) point. To test other metals, first plate copper over the entire strip at 100% (2.5 sq in == 250 ma) for about 30 minutes. Cut coupons of this for testing silver or nickel. To check a gold bath, plate a 10 minute layer of nickel over the whole copper-plated strip and then cut the coupons for gold tests.


ELECTROCLEANING

When plating is halted mid-process and allowed to DRY, it may lose activation where the next metal layer won't plate or adhere to the first. The fix is to electroclean (follow the suppliers' instructions), rinse well and follow with an acid dip and final rinse. Electrocleaning solution is a fairly strong alkaline cleaning bath. It works by applying a strong current using a stainless steel anode (work is the cathode) to get a clean surface, rinsing well and then acid dipping to re-activate the existing metal. No guarantees.


TARNISH, ANTI-TARNISH AND PATINAS

Both freshly plated copper and silver seem to have a high surface activity and it appears that they tarnish easily. Consider that plated lapidary surfaces could be really difficult to polish. As a last step in the process, a dip into an anti-tarnish solution (and final water rinse) has proven to be a good step. Dalmar Mfg offers a solution (#C-9) as well as Rio Grande (#335-037). Rhodium plating solutions (non-cyanide) are also available which give a non-tarnishing top plate which, in theory anyway, is very abrasion resistant. At more than double the price of 24kt gold, rhodium is a serious anti-tarnish agent.

For the more crafty lapidists, all the colorful power of copper patinas and silver aging solutions can also be employed with this process.


Constant Current Regulator Diagram:

[current regulator diagram]



DISCLAIMER

I am not employed by, and have no commercial interest in, any vendor mentioned in this document. I have no formal training in occupational health or safety and all statements herein represent my personal understanding and practical experience. Anyone using chemicals or apparatus referenced in this document, do so at their own risk and liability.
1/5/98 v3.3
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