Glyph, thanks for the awsome reply!!
I'm not too concerned about the shape of my copper "lump" when its done. I want it to be interesting to look at. Not a perfect cube or anything.
An lump of copper that looks like an alien lifeform might fit the bill
How do I figure out the right sulfuric acid and copper sulfate mixture? Trial and error? Is this mixed with water? Will the acid mixture last a while, or does it depleate and have to be changed though the process?
The mixtures are available online, high acid ratio solutions (also known as "high throw") tend to be around 180g of sulfuric acid and 60g of copper sulfate added to 1L of water. High copper solutions tend to be around 210g of copper sulfate and 20-30g of acid per 1L. These numbers though are not "sweet spots" and actual ratios can vary greatly. The additives you add tend to dictate the concentrations since the additives are chemicals and therefore require a certain chemical environment to function properly.
If you are using no additives then the process can be very forgiving and you can just dump in acid and copper any way you want and still get plating if you just adjust your current accordingly.
As for how long it lasts. Once again the additives play the key role, they are the ones that deplete and change the makeup of your bath as time progresses. some additives will breakdown even without usage and so your plating bath will have a limited shelf-life.
In the case of no additives, technically the bath should last forever. This is because unlike most other metals in plating, copper plates with 100% coulombic efficiency. Every atom of copper that plates into solution from the anode is equally accounted for by an atom copper plating out of solution at the cathode. So even if you pump a million pounds of copper through the solution, it should technically remain the exact same composition as when you started (acid does not get affected by plating, it just helps the movement of ions and conductivity). However, real copper is not 100% pure. There will always be tiny bits of iron or other metals that plate into solution, but will not plate out. Over time these build up and contaminate your bath. But this a minor issue if you maintain clean practices and filter your bath often. I was able to run my baths continously for several months and contamination never became an issue. Although i still recrystalized my bath after that time just because i like the mental feeling of knowing i've got pure materials.
Do you have any suggestions on what a hobbiest like me could use for a power supply? I was thinking of an automotive battery charger, but that wouldn't allow me to control the current very much.
Around these forums you will find designs for constant current power supplies, i suggest you start there.
Personally I built my own switch-mode constant current power supply.
I do know that most casual platers get away with simply getting a giant unregulated power supply (transformer, diode bridge and capacitors) and then adjust the output with a variac. They watch the current through a shunt resistor. This method has the problem that the current isn't stable and might change as the shape of your object changes during plating.
Others use giant high-wattage resistors to control the current.
How is the filtration done? Is it sorta like a pool filter that is just circulating the solution though a filter?
yeah the concept is similar. but the practicality is different. You're working with a solution that is highly acidic and corrosive and has copper sulfate which damages even stainless steel. most pumps will dissolve and leave crap into your solution if you use them. The high-quality pumps for corrosive fluids cost hundreds to thousands of dollars.
Most platers doing just plating (no electroforming) get away with just pouring their whole solution through a coffee filter every few days. This does run the problem that the coffee filter itself will breakdown and release contaminants into your bath.
Personally, I adapted a plastic aquarium pump to do my filtering continously.
Keep in mind: the primary source of particulates is the anode itself. As the copper anode dissolves it will drop off flakes of black copper that float around the solution. Therefore most platers place their anodes in a special porous bag that traps the particles but still lets ions flow through. A good bag will greatly reduce filtering issues.
What time frame am I looking at to take a couple pounds of scrap wire and make a couple pound lump? A week? a mouth? Way longer?
depends on what type of bath you're using and what addtives you add. A high quality mix of additives with good bath agitation, continous filtration and precision current control can easily plate a quarter inch of mirror finish copper a week, maybe more (but i've never pushed it).
you could probably make yourself a nice copper plaque in a couple of weeks or so.
Something with no additives, no stirring and no filtering will take a long time. I was able to pull about half-milimeter a week with that setup. Pushing it further with more current only caused massive treeing that gave me a red "rock" that looked nothing like metal.
Sorry to bombard you with questions. I'm just glad to see somone here knows about this!
Remember, safety first, if you have little ones running around or moronic siblings keep this setup out of their reach. You will make a mess of the area you do it in and this unique combination of acids and metal salts will damage things you thought couldn't be damaged (i found that out the hard way).
While i don't normally plug particular companies, here is a company that sells complete plating kits (including those wonderful chemical additives)
Plating Kits Electroplating Kits Aluminum Anodizing Kits Powder Coating Systems Metal Polishing And Buffing Supplies - Caswell Inc.
they even include the bucket!
Personally i made all of my own equipment and brewed up my own additives (i'm a chemist) so i never used plating kits and can't really comment on quality. However i've heard nothing but good things from my friends online. Although plating suppliers do tend to overcharge for additives since they are so important and few people understand them. I saw one company charging $100 for enough additives for 500 amp/hours of plating. Personally I can brew the exact same additive for $23 that gives 10 amp/YEARS of plating. So beware of additive price fixing if you decide to use them.
Have fun, and don't sniff the fumes
