Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ

The authoritative public forum
  for Metal Finishing since 1989
  

How to calculate/estimate the cost of gold plating

Q. We produce silver jewelry in Bali. Some of our earrings we gold plate, but the cost of plating became expensive. We bought a gold plating set-up and we are now gold plating ourselves, and we are trying to figure out how to cost each piece we gold plate.

If anyone can help me figure this out will be very much appreciated.
Roma

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September 3, 2009

"Gold Plating Technology"
by Reid & Goldie
(hard to find & expensive; if you
see a copy cheap, act fast)


on eBay or

AbeBooks

or Amazon

(affil links)

A. Hi, Roma. Gold is of course a precious metal that is priced by the gram or the troy ounce. So first, you need to know how much gold you are applying to each piece. For this step you can multiply the surface area of the piece by the thickness of the gold, then multiply by the density of gold to get the weight. Preferably, in addition to this, an ampere-minute meter is very helpful because the amount of gold deposited is directly proportional to the ampere-minutes that you plate for (the current multiplied by the time). You can look up Faraday's Law for a better understanding of that.

Once you have the amount of the gold you have applied, you can multiply by a factor representing the extra cost for the proprietary gold plating solution over the cost of gold metal. For example, if a liter of the solution you buy contains 2 grams of gold, then your cost for two grams of gold is the cost of a liter of that solution. Finally you add a labor, overhead and profit factor. If I have lost you, please ask for clarification on the step in question. Good luck!

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

Cost per part for silver plating

I'm an engineering student working on a project involving silver electrodeposition. I need to calculate the cost of silver per part using a silver cyanide plating process. If I were to use a barrel plating process and silver nuggets for the anode is there a formula to calculate cost of silver required per part? I am sure you need to factor in square footage and desired plating thickness, but how do I factor in such things as dragout costs and plating efficiency? What are the current prices for both copper and silver anodes? Any help is appreciated. Thanks!

Hello Michael,

Price of Deposition:

- Surface of part to be plated
- Thickness desired
- Amps in Use
- Plating efficiency
- Voltage (electricity calculation = Watts or kWh)
- Energy costs (heating, stirrers, motors etc)
- Time running through costs
- Water flows of rinses gpm
- Side costs (maintenance, air, DI-Water in use, Waste treatment)
- Preparation time of barrel, Labour costs
- Important => Quantity of pieces are to be plated per annum
- Profit percentage to be wished
- Administrative costs

Just an overview a bit....for a guesstation :-)

Multiple threads merged: please forgive chronology errors and repetition  🙂

Our cost exposure due to gold cost in plating of watches

Q. We are a direct mail order company who sources watches from China. What we would like assistance with is understanding a number of things:

#1 is if our specs are adhered to which is a 1 micron thick plating of 18k gold how much impact to our cost is every $25 USD movement in gold?

At $1850 USD gold, we believe the cost of 24k gold should be just a fraction under .06 cents. so, 18k gold would be approx 75 % of .06 cents/mg.

What we are not sure of is how to calculate the area of the case/band & clasp to calculate the total dm2 to then be able to convert to mg and then calculate what our cost would be at different gold prices.

We have asked our supplier these questions and are not getting a reply that is logical or makes us comfortable. You might say that we may be shopping for a new supplier at the same time.

#2. what is the most cost affective way to confirm that your specifications of gold plating are being met? Our current method is quite cost intensive to send to a metallurgical company.

#3. Should we source each step ourselves and contract an assembly point?

XRF Coating Thickness Analyzer

on eBay or

Amazon

(affil links)

A. Hi, Phil. I agree that you can't function without knowing both how much gold is supposed to be on the watch and how much actually is. Frankly, I'd be very surprised if your vendor doesn't know exactly how much gold is on the watch because they have several ways to tell (for example, gold purchase records, amp-hours consumed, thickness testing, and perhaps stripping), and a lot of incentive to know (few are so trusting as to operate a precious metals operation without good inventory control as a guard against theft).

#1. At 1 micron thickness (40 microinches), you would consume 1 cubic inch of gold in plating 25,000 sq. in. of product. Gold weighs 10.16 troy ounces per cubic inch, so the gold would cost you $.75 per square inch if 24 karat, so your $.06 sounds way low. At 18 karat it would still cost you $.56 per square inch, and as a 1st cut wild guess the area would be around 8 sq. inches. Sounds to me like you are low by a factor of about 100 :-)

#2. You can test the gold thickness with various instruments like x-ray fluorescence, and you can determine the total gold usage per watch by stripping, refining the waste products, and weighing.

#3. I can't help with #3 and I doubt that anyone can without a lot of investigation. Good luck.

Regards,

Q. Sir
I want to know how I can estimate gold plating cost of jewellery.

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A. Hi cousin Vishal. Step 1 in review: What is the surface area of the part and the thickness or the gold, or alternately, how many ampere-minutes do you plate it for? You can only proceed to step 2 when you have the answer to step 1, either in grams of gold or ampere minutes applied. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
July 18, 2013

Q. Hello ~ I would like to know how much it would cost to have a heart pendant plated in gold, it has other different metal alloys in it! It is actually a tiny urn; my Moms ashes are in it! A gold pendant/urn was not available at the time! I would have chosen the gold! Now, I have a different problem, the bale came off and needed to be glued back on. Well, the funeral home glued it back on but glued it on backwards so the metal doesn't match! So, the only solution I could think of was getting it gold plated? The size is 1" X 1"

Would it be reasonable in cost or should I get it silver plated instead? I am not a silver type person ... I love yellow 14kt gold!

Sincerely

A. Hi Sylvia. The previous Q & A's on this thread seemed to involve manufacturers and production plating of gold. When you want one small item plated, it's mostly about the labor cost, not the material cost.

Just as there won't be much difference in cost whether your plumber has to replace a 3/4" washer or a 1/2" washer to fix the dripping faucet, there probably won't be much difference in the cost of gold plating vs. silver plating because most of the cost will be in handling the order, and the labor of polishing, cleaning, and plating. Most plating shops will have a minimum charge or "lot" charge of $25-$250, which will probably cover it whether you choose gold or silver plating. If you can't readily find a plating shop to do it, a local antique dealer may have arrangements with one. Please inform them about the glued bale because the plating process might dissolve the glue. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
January 2015

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April 29, 2018

A. Hi, gold plating is cheap. It is incredibly thin. Greatest property of gold is ability to be spread/plated as thin as 30 atoms.
1 micron is 10,000 atoms thick.
That's 333 times thicker than needed.
Problem is gold platers know people are ignorant.
We pay as low as $.06 per part for gold plating. We gold plate everything we can.
example:

gold deposited at 1 micron x 160.9 x 33.5mm = .0054 mm^3.
gold density is 19.3 g/cm^3, which is .193 g/mm^3
amount of gold = .193 g/mm^3 x .0054 mm^3 = .001 g
gold price today is $42.36 per gram.
gold cost: $42.36 per gram x .001 g = $.042
double this for grins.
$.084

You can get the plating labor by looking at any process, say $.20 each to plate anything, qty 100.
Parts get dipped into a tank, no labor other than 22 seconds to dip, 5 seconds to monitor, 34 seconds to remove, 15 seconds to clean & inspect.
example:

A gold plating shop collects $300 from you for $.92 gold and labor x 100 pieces -- $208 profit.
if 25 orders a day x $208 profit = $5,200 a day.
Laborers $9/hr, varies.

Somebody is greedy.
Yeah yeah yeah, plating shops have very low overhead; most are located in old buildings in high crime areas.

vern stoffel
- superior, Colorado usa

Q. Hi Vern,
I am new to plating. Setting up shop for jewelry so please excuse my ignorance.

So surface area of 160.9 x 33.5 mm I am assuming this is a flat surface and it is in millimeters?

g/cm^3 - What does this mean exactly?

.0054 mm^3 - What does this mean exactly?

Thank you in advance,
Roberto

Can somebody give me a rough estimate as to what the gold plating price might be?

Q. So I have a tiny little USB with a 2-part case (one of the ones you rotate to open) and I want to get it gold plated, along with 4 smaller metal pieces, really tiny like a tiny keyring and stuff like that that links necklace parts together.

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A. Hi Benjamin. Unfortunately, onesy-twosy pieces like that require individual logging, inspection, possible polishing, planning & scheduling, racking, handling, and packaging. A lot charge of $25-$250 would not be unexpected even if the cost of the gold is but a few cents.

But hopefully Vern will open a shop and do the job for a quarter :-)

The thing he is very right about, is that production volume largely controls the cost. You can probably get 10 of each plated for that same lot charge; and if the order were for 100,000 and the gold plating quite thin, it might cost just pennies each.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
December 2018

How much area will 4 grams of gold cover?

Q. Hello,

I'm an electroformer in the jewelry industry and I have recently started plating my pieces in finishing plates at 3 micron thickness. My solutions for (gold) as an example contain 4 grams of gold per liter. I'm trying to figure out what area or how many square inches 4 grams of gold can deposit or cover at 3 microns thick.
I can't wrap my head around an equation with the tech sheet info for the solutions I use. I would like to track my usage if possible to avoid the dreaded poor plate job by accident as the solution begins to drop off.

Can anyone lead me to some help? I'm extremely right brained and have a very difficult time with figuring things like this out. If I have an equation I can apply it to all of my solutions. Thanks in advance for the help.

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A. Hi Annie. Gold weighs about 19.3 grams per cubic centimeter. That means if you had a small gold dice cube of size 1 cm x 1 cm x 1 cm, (i.e., with a volume of 1 cubic centimeter), it would weigh 19.3 grams. So 4 grams would theoretically fill a volume of 4/19.3 cubic centimeters or 0.207 cubic centimeters.

Volume is area x height, (i.e., area x thickness). So theoretically 4 grams can plate an area x thickness totaling 0.207 cubic centimeters. If the thickness is 3 microns, i.e., 0.0003 cm, then the area you can plate with that much gold is 0.207/0.0003 = 690 square centimeters (about 106 square inches).

So I guess the formula you could use is 4 grams of gold will cover 100 square inches at 3 micron thickness.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
December 2019

  Thank you so much for this incredibly helpful and thoughtful response! I can't wait to apply this to all of my other solutions and tech sheets. Thank you Thank you!

Annie Swincinski [returning]
The Mantra Life - State College, Pennsylvania USA
December 4, 2019

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A. Hi Annie

If I could expand a little on your question.

The density of gold is 19.3g/cc but when plated it incorporates some organic matter and often other metals to achieve a specific colour 18 kt etc. It is difficult to measure but the best estimate from many experiments is about 17.5 g/cc. Put simply, your 4g will spread a little further.

With most plating solutions the anode dissolves to replace the metal plated out and the concentration in solution remains more or less constant. Gold uses inert anodes so the metal in solution reduces and is replaced with "gold salts". The gold in solution is a fixed cost and the salts used are the running cost. If you allow the gold in solution to reduce without replenishment, the efficiency of the solution will reduce.

It is very difficult to get completely even plating on any part. It will normally build up at edges and be thinner in recesses so remember that your calculated thickness is an average and may be challenged by someone with measuring equipment. How do you measure thickness?

Please consider using consistent units. Calculating in both microns and square inches only needs one small error to become a very expensive mistake.

Geoff Smith
Hampshire, England
December 6, 2019