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How to get heavy gold plating (5 microns+)

Q.
**1) Could the expert kindly advise:**

a) When preparing a decorative gold plating solution with the following formula:

- HAuCl4
- CuSO4
- NTA
- K3C6H5O7
- KH2PO4

Should the pH be maintained at 3.5 or 3.8? (Note: The pH must not be higher than this range because if the pH exceeds 4.0, the gold plating solution using HAuCl4 as the gold salt --without free cyanide-- will precipitate and hydrolyze.)

**2) When preparing a *thick* gold plating solution with the formula:**

- HAuCl4: 3.75 g / 1 liter
- Citric acid: 30 g / 1 liter
- H2SO4 (10%): 20 ml / 1 liter
- Conductive salt NH4Cl: 5 g / 1 liter
- Brightener additive (Saccharin): 2 g / 1 liter
- Distilled water: Top up to make 1 liter

Does the preparation procedure for the thick gold plating solution differ from that of the decorative gold plating solution?

For example:

a) I plan to dissolve 1g of HAuCl4 in 200 ml of distilled water, then adjust the pH to around 2 or 1.5 (i.e., lower than 2) -- This is Solution 1.

b) Then, dissolve citric acid (C6H8O7) in 500 ml of distilled water -- This is Solution 2.

c) Next, gently pour Solution 1 (gold salt solution) into Solution 2 (citric acid solution) and mix well.

d) Then add H2SO4 and stir well to stabilize the thick gold plating solution.

e) Next, add the conductive salt NH4Cl.

f) Add the brightener additive Saccharin.

h) Finally, adjust the pH and top up with distilled water to make 1 liter. (Or top up with distilled water first, then adjust the optimal pH -- 4, 5, or 6 is acceptable.)

**Question:** Among the two pH adjustment methods above, which one is more appropriate?

**3) Could the expert please clarify:**

- For decorative gold plating, the pH is typically maintained between 3.5 and 3.8. (If pH exceeds 4.0, HAuCl4 in the solution will hydrolyze.)

- For *thick* gold plating (as per the above formula), the pH is allowed to be around 4.0, 5.0, or even 6.0.

**Question:** What is the main difference between these two plating processes and formulas (thick gold plating vs. decorative gold plating)? Thank you very much for your guidance.

**4) Could the expert kindly provide the full process parameters for thick gold plating using the above formula:**

- Ideal temperature for thick gold plating?
- Voltage?
- Amperage?
- Anode connection: Should the (+) anode be connected to stainless steel, titanium mesh, or 9999 pure gold? Which option is the most effective?
- Should the solution be stirred (magnetic stirring) or not?

And in the unfortunate case that the thick gold plating solution (prepared without free cyanide, as in the given formula) results in a dark or black finish rather than a bright gold appearance -- what is the likely cause?
How should the process or formulation be adjusted to achieve a bright, shiny, yellow-gold finish on the plated object?
Thank you expert

Thuy Nguyen
- Ho Chi Minh, Vietnam
April 21, 2025

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⇩ Related postings, oldest first ⇩

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Q. Hello Sir,

I have been told that with flash gold plating solution there is a way to get 30-50 microns of gold onto jewelry. A person told me he have looked in a 'history of plating' book, he found that if you put about 5 times the normal amount of gold into your bath, lower the voltage and increase plating time, you can plate that thickness in an hour or so and have it come out bright. This will give a very thick and durable coating of gold. Is it possible or not -- please advise me?

I want to plate 30 to 50 microns of gold on a watch. Note:I'm not talking about 30 to 50 microinches.

Thank you,

Dipen Pattni
jeweler/goldsmith - Dar-Es-Salaam, Tanzania
2002

Q. Dear Ted,

I don't know the type of bath, but I'm buying solution from my supplier and I'm adding 68% GPC in the instagold flash bath 2 grams per gallon.

My supplier is telling me you can plate but you have to add brightener and 1 oz of GPC per gallon and you will need lot of agitation then I can plate very thick.

I want to plate 50 micron on watch, base metal is brass and SS. Please advise me is it possible or not, or I need different type of bath?

Thanks,

Dipen Pattni
jeweler/goldsmith - Dar-Es-Salaam, Tanzania

Q. Dear Ted :)
I know you read and listen and watch. I'm sure that my bath is not a cyanide strike bath. Anyway I'll spend 1 oz of GPC and brightener to let see what happens ;(

My supplier is Gold Touch [a finishing.com supporting advertiser] they have advised me a lot but they have never done heavy thicknesses like I want. So I thought let me post the question on finishing.com, masters like Mr.Ted or others can help me. My english is not good, please try to understand.

Thanks,

Dipen Pattni
jeweler/goldsmith - Dar-Es-Salaam, Tanzania

Q. Dear Mr. Ted,

Solution powder itself does not contain the cyanide, type of bath is acid gold bath that is both electrolytic and immersion, pH is 4.4 to 4.8.

Thanks,

Dipen Pattni
jeweler/goldsmith - Dar-Es-Salaam, Tanzania

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Multiple threads merged: please forgive chronology errors and repetition  🙂

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Q. I don't seem to be able to get a straight answer from my supplier. I'm currently using a cyanide based gold plating solution. This is one of the common solutions used in the Jewellery business. I'm gold plating base metal rings and I cannot get a thick coat of gold deposit on the items. The directions for the plating bath are the following:
Heat at 130-140 °F and plate with 5-6 Volts for about 15-30 seconds, using a Stainless Steel anode.
By doing that I only get a flash and sometimes when I lightly buff the piece with a cloth the plating goes away. I tried to lower the voltage to 2.5-3 Voltage and increase the plating time to about 1.5-2 minutes. The same happens. And when I plate for about 5 minutes the plating becomes too dull and dark.
Another company sells a K24 gold plating solution that according to what they say it will plate 2 microns in 2 minutes. And if I need to pate thicker just leave it longer and then wipe the piece to remove the dull finish. I don't know if I can trust this.

Any ideas? I need to have a bright thick gold plating that will last for years. A plating I can engrave on.
Thank you in advance for your time.

Pierre P [surname deleted for privacy by Editor]
Jewellery and watch case plater and refinisher - Montreal, Quebec, Canada
September 12, 2008

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Readers who are interested in the formulation of baths, and the operational considerations, for very heavy gold plating may also be interested in these related threads:

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