Brightener for acid copper plating

A. Hobby beginner electroplater here. I have found an easily available (in the US anyway) brightener that works for me using sulfuric acid based room temperature bath. MiraLAX, which is a laxative found in any drugstore or Walmart. It is basically polyethylene glycol powder and worked great for my needs.

I too searched for a long time for a brightener. Dosage is approx. 1 teaspoon per gallon, but I have not determined the optimal amount since it worked for me right away. FYI 0.2 volt.

A. With respect to the question on brighteners, polyethylene glycol has been mentioned. The laxative recommended (in fact all PEG laxatives) has quite a large molecular weight, i.e., 3350. What is recommended for plating seems to be lower molecular weight, i.e., shorter chain molecules.

The other brightener I've read about is "Dalcin(R)" aka sodium saccharin. It can be purchased in bulk from eBay quite cheaply.

Sodium Saccharin on eBay or Amazon (affil link)]

(I understand the chef analogy to requests for proprietary formula ... but the analogy seems to fail when we forget the original poster isn't telling the chef to release his recipe, the OP is asking ... and asking politely it would seem).

Thanks
Doug

A. I am just getting started with copper electroforming and have found the many YouTube videos by Jason Welsh most informative. He discusses the use of Polyethylene Glycol (PG) as a brightener and points out a practical issue. Over time you will find that you need to keep topping up the PG in your tank. Eventually this will no longer restore brightness to your pieces. The remedy for this is to pass the entire solution through a carbon filter. After filtering it would be prudent to check the pH and adjust the acidity as required.
Jason's video "Electroforming Brightener Glycol":

I realise that this relates to Electroforming rather than Electroplating but think that it is still usefully informative.

Thanks Jeremy, that is very practical & useful information for non-commercial use, as well as for third-worlders who lack access to established brightener supplies.

Still, there are some differences between artistic electroforming and commercial electroplating. For example, there is little or no need for ductility in electroforming, but it is often essential in electroplating: when automobile grill expand & contract as they fry in the sun or trudge through slush, a ductile copper layer between the chrome plating and the plastic substrate is crucial.

Another issue that hobbyists usually do not need to worry much about, but which is critical for commercial platers, is an 'equilibrium process' -- for them it is not just a matter of the plating on one component functioning well, but that the bath stays properly balanced so the second part will plate right, and the million-and-oneth component as well.

Luck & Regards,

A. You may begin by consulting a variety of reference books and reading old and current patent literature. Then you can go to the laboratory and test out each of the formulation components until you arrive at the components needed and the quantities required of each. Or, you could call a supplier of proprietary materials who has already done the above and more and would charge a fair price for the benefit of their research and knowledge by selling a proven material.

You might surmise that I am involved in the sales and/or manufacture of proprietary chemistry and you would be right. Do you tell a chef to give you the recipe, you don't want to eat at his restaurant? Do you ask a doctor for the formulation for a drug? Why do you expect to get proprietary knowledge for free?

Hello Gene, you're clearly right that some knowledge is proprietary ... but we should probably be gentle. People may not know what is generic vs. patented vs. trade secret, and the other ins-&-outs of the Western plating industry, and may simply assume that what they learned in science class is how plating is actually done.

"Home-brew", however inferior, is required where there is no commercial distribution of western plating processes (and even in the West when a technology loses its champion -- as happened with sulfamate nickel, cyanide zinc plating, and magnesium finishing processes).

There is a worldwide patent system, the purpose of which is "to incentivize the advance of technology for the good of mankind, by granting temporary financial benefit to those who put in the work"; we are welcome to try to hold information as proprietary forever rather than patenting it, but needn't be offended that people don't inherently understand our business model.

Thanks for helping where you can, as you often do!

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

"Modern Electroplating"
by F.A. Lowenheim

on AbeBooks

or eBay

or Amazon

(affil links)

A. Hi, Eric. I understand. Unfortunately, I and the majority of readers don't know the answers anyway because they are trade secrets, and you won't find current information in text books these days. In some cases, those brighteners can't be created by simple mixing of raw materials anyway; rather they must be "synthesized from precursors", similar to how plastics are made from crude oil -- which rules out "home brew" anyway.

A possible path forward may be to look through old plating books for generic brighteners from "back when". Lowenheim's "Modern Electroplating" from 1942 includes a 2-page discussion of generic brighteners, and it references many different articles on the subject, including many patents, most of which are surely expired by now. (Access to patent info is generally free and reasonably easy these days).

It's not as simple as "try this" though, because each of the referenced possibilities has a list of operating parameters, disadvantages and warnings, etc. Here is an excerpt from that discussion to show the flavor of it:

Best of luck!

Regards,

A. Have you tried Thiourea ⇦ this on eBay or Amazon [affil links] ? Use it sparingly. Be very careful, this thing will give you pancreatic cancer and damage your bones.

A. Urea 1 g/l and glycerin 1-2 ml/l

A. Hi, Saravanababu. Without brighteners, copper plating may grow as rather large crystals in the way of rock candy. These tend to be rather soft, and porous (because there will be 'holes' where these large crystals grow to meet each other), and dull (because of their rough topography).

I don't pretend to truly understand the stereochemistry of exactly what goes on, but brighteners tend to deposit with the electricity, and thus to shield high current density areas first and, by so doing, help to even out plating thickness, and to promote the growth of new crystals rather than enlarging the existing crystals. The process leads to more, smaller, harder, less porous crystals, and brighter deposits. Good luck.

Regards,

A. Hi, Komal
Sorry, I don't know the exact answer to that, or even if there is a universal answer, because different proprietary brighteners might react differently to temperature. But I do know that some brighteners "oil out" (break down into ineffective oils) at temperatures as low as 100 °F, and maybe even lower. Sorry, but I don't know the composition or temperature resistance of the proprietary acid copper brighteners. Good luck.

Regards,

A. Hi Omid,

Usually is some polyalkylene glycol related chemistries.

Regards,
David

A. Hard copper brightening is cobalt sulfate.

A. Hi Rameez. We appended your inquiry to a thread which explains brighteners for acid copper plating. Good luck.

Regards,

Blackstrap Molasses

on eBay or

Amazon

(affil links)

A. Surprised no one mentioned molasses. That's right, blackstrap molasses from the grocery store.

Q. How do molasses work are they in tank or applied post plating and how, etc.?

A. Hi Brock. Molasses is a 'brightener' for copper plating; as such, a small amount is added to the solution in the plating tank. Molecules of the brightener are drawn to the high current density areas of the component being plated and tend to slightly shield it away from further plating. By doing so, the plating is more even in thickness, and more adatoms form, for smaller, less porous, harder plating.

Regards,

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

Q. Delighted for your answer, thank you - is there a go to document on hobby plating, I'm just getting a lot of mush even with low volts and amperage if the thing I bought on eBay is correct (there is only mild fizzing) -- also I'm using copper pipe as anode, and graphite mixed with waterproof PVA for cathode object - is this suitable and/or is there anything else with better conductivity?

"Electroplating Engineering Handbook"
by Larry Durney

on AbeBooks

or eBay or

Amazon

(affil links)

A. Hi again. For a "go to document" see if a local library has the Electroplating Engineering Handbook ⇨

A copper pipe is a poor anode, but it may be useable for hobby purposes. For hobby plating, as opposed to production plating, the pure copper of stripped wire is probably best. Production platers need phosphorized copper anodes (because otherwise the copper concentration builds up relentlessly to where the anodes go 'passive' and plating isn't possible).

One of your issues is that there are a hundred variables in plating, so when you have questionable anode material, questionable cathode, questionable power supply, questionable solution chemistry, questionable instructions, and are getting "mush", it's already a very deep hole to climb out of, and you don't want to start pouring questionable brighteners into that hole :-)

Personally, I would start by getting some small pieces of brass sheet, get them spotlessly clean by scrubbing with a pumice ⇦ this on eBay or Amazon [affil links] and detergent solution and toothbrush while wearing gloves ⇦ this on eBay or Amazon [affil links] , and try to plate them, because brass is the most plateable substrate, whereas we have no idea whether your particular graphite + PVA article is even plateable. The way forward is to narrow down the list of things that could be causing the problem, successfully or unsuccessfully plating something which is much easier to plate. Good luck!

Regards,

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

  Thank you again Ted, Yes I thought it could be any of a number of individual or cumulative factors! Going to start afresh, thank you for your advice, best regards. Brockie

A. Hi Joshua.
Even production platers generally can't analyze for brighteners and must rely on Hull Cell testing (search the site) to determine brightener additions. But it's a very small amount, probably nowhere near a milliliter for a one liter bath. You need sulfuric acid ⇦ this on eBay or Amazon [affil links] as well as the copper sulphate, and ideally about as much thiourea ⇦ this on eBay or Amazon [affil links] as molasses.

Luck & Regards,


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