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Meccano restoration - Plating

For the previous page on stripping and preparation, click here.

Brassware

There are four significantly different methods of cleaning brass that I've come across and tried.  None are completely satisfactory as far as I can see, but here we go anyway...

Cleaning solutions

The first way is to use some sort of cleaning solution.  The 'standard' one is to use very hot water, in which you have dissolved a spoonful of tartaric acid (e.g. cream of tartar), and a spoonful of washing-up liquid.  This does clean things a bit, although it doesn't fix serious tarnishing, nor does it clean inside all the gear teeth (you have to scrub with a toothbrush for this).  You need to agitate the parts, which can be done with a tumbler.  It doesn't solve corrosion issues with brass nuts and bolts, and it can leave a white deposit in the screw threads in my experience.  Some recommend a product called 'Horolene', which works in a similar way.  The most serious downside, however, is that if you leave the items in the solution too long, the brass turns a horrible coppery colour.  This is only a surface artefact, and you can solve it with any of the following three methods, but it's awful when it happens.  For all of these reasons, it might be the easiest way to clean half a dozen gears, but this doesn't seem to be the way to work on a large quantity of brassware.

Tumbling

Another simple technique I'm trying at the moment is tumbling.  Either use a commercial stone tumbler, or you could easily make a Meccano device consisting of two axles side by side, each with a pair of pulleys and 1" tyres (making a space that a jam jar sits on), and drive one of the axles with a motor of some kind.  The trick is to find the right size of container, and the right abrasive.  I've tried things between very fine sand and sodium bicarbonate (in water, of course).  Abrasives too coarse leave a pitted surface on the brassware.  But the main problem I find is that the gears themselves bash against each other, rounding off the edges of the gears.  I'm sure they still work if this happens, but they look silly.  I haven't yet found an abrasive that gives a good finish, although I'm yet to try things like walnut shells that might work.  This is still a work in progress, but I'd really appreciate any suggestions you have!

Buffing

This involves a cotton buffing wheel, a heavy pair of leather gloves, and the appropriate 'soaps' that go on the buffing wheels of various grades that will start by cleaning and end with polishing the brassware. The results you get are incredible – you can see your face in the parts.  However, this isn't how they're supposed to look and so I'm not so keen on it.  There are several parts that are really tricky to do in this way (socket couplings, for example), and you can't do nuts and bolts at all.  You soon find out which of your bush wheels are in fact brass plated steel and not brass (so you have to check with a magnet first!) Most of all though, it's a lot of work if you have a load of parts to do.  I've given up cleaning brassware this way, although I do still use my buffing wheel for parts that have both brass and nickel plate on them (and no way of separating them).  This pretty much comes down to pawls, end bearings, and small fork pieces (and their derivatives). 

Electropolishing / electroplating

Electroplating is obvious – you clean the brass with solvents and degreasers but don't care what finish you get.  Then you add a few atoms of new brass, and you have a new-looking part.  Electropolishing is similar, except that you reverse the process and remove the top few atoms of brass from the surface (taking any tarnishing with it, generally).  Both end up looking identical, although electroplating is cheaper and therefore we'll probably stick to it.  However, this can't sensibly be done at home, and you have to wire up (electrically connect and hang up) every part.  If you don't do this yourself, the plating company will charge you per part.  Fine for socket couplings, not so fine for nuts and bolts.  So you need to ask "can you do barrel plating in bright brass?" to every electroplating company you can find.  When you find one that does, the question is about how big a load can be – you pay for the load not the parts.  So you can fill up a load for a fixed price, which is great.  Unless you only have a few parts, in which case you're paying for several kilos. 

Apart from this downside (needing to send off a fixed load quantity and wait for it to come back), the results are very good.  They're not perfect.  My biggest problem is that the parts come back too clean, so they don't look absolutely genuine.  On the other hand, the nuts and bolts come up great too, and you can even brass-plate things that weren't supposed to be! The effort involved is almost nil even for a huge quantity, which is a great plus point in my book.  Just check out the before and after photo and make your own mind up.

Nickel plating

Some background

There's a lot of confusion about the nickel-plating process, and what makes Meccano nickel parts dull or bright.  Time for a bit of history, I believe.  And an attempt at some clarification.

Let me introduce two important chaps in the history of nickel plating.  Mr Watt, and Mr Watts. You will no doubt have heard of a Mr Watt, but it's not James Watt of electrical power naming fame.  I'm talking about a Mr Alexander Watt, who wrote several papers and books, including "A practical treatise on the electrolysis of gold, silver, copper, nickel, and other metals, and alloys" in 1889.  This happened to be the same year that Mr Oliver Patterson Watts graduated, and Watts subsequently became something of an expert in the electroplating field, in the faculty of the University of Wisconsin. 

Did we need to know that? Well, I think perhaps yes, so we can understand the confusion that arises.  In April 1913, Oliver Watts wrote a paper for the American Electrochemical Society after he had been requested to summarise all the various processes that were in use.  In this paper ("The Electrodeposition of Cobalt and Nickel") he describes dozens of different processes and mentions some of their pros and cons.  Among these are references to "fifty different nickel baths tried by Alexander Watt".  Mr Watts happily refers (in 1913) to a Watt's bath as a fairly generic term for a nickel-plating bath.

In April 1916, Oliver Watts wrote a paper entitled "Rapid Nickel Plating".  In this paper, he mentions "a solution that is extensively used", consisting of nickel sulphate, sodium chloride, and boric acid.  He proposes a better system with two changes: heating the electrolyte to around 70°C; and substituting nickel chloride for the sodium chloride.  In his experiments, these changes allow a much faster electroplating, with less tendency for the plating to peel off the final product.

Ever since this point, the "Watts bath" has been the standard method of nickel plating, and nowadays refers to the basic consistuents of the electrolyte.  However, it should correctly be referred to as "Watts' electrolyte", since a "Watt's bath" (by Watts' definition) can apply to all sorts of inferior methods.  Got it?  Good.  Ms Truss would be very happy that we now have the apostrophe in the right place.

All we have to do is remember that it all changed in 1916.  Watts worked out the new system, which is now universally known as a Watts bath, but that wasn't the correct term at the time.

Back to Meccano.  Graham Jost provides Frank Hornby's description of the process:

Lovely, except that this is clearly the pre-Watts process.  No mention is made of heating the baths, and "a chloride such as common salt" is used.  Of course, this is the process that would have been standard when Meccano started nickel-plating parts, and Frank Hornby was involved in the day-to-day production of Meccano.  The process took hours instead of minutes, which seems clear from the way it is written.

Back to Mr Watts.  In his paper of 1913, he refers to all sorts of problems encountered with nickel-plating parts (in the way that Meccano was doing it at the time).  In particular, he describes how the initial nickel plating is quite bright, but as the thickness increases the finish tends to dull.  The thicker finish is desirable (as it is tougher, and tends to fill imperfections in the metal).  However, with the processes in use at the time, thicker nickel deposits were brittle and tended to 'flake' off the surface.  Watts quotes various sources such as:

• McMillan: "Nickel well deposited is extremely hard, so hard that it cannot be burnished, and is somewhat brittle. Thick coatings are especially liable to flake off in use, unless exceptionally well deposited, and even the thinnest films will part from surfaces which are not chemically clean."
• A. Hollard: "The difficulty of obtaining thick nickel deposits is due to hydrogen evolved along with the metal and absorbed by it, causing brittleness."

Hypothesis

Obviously, prior to 1916, Meccano would have used the pre-Watts system of nickel-plating.  This entailed risk of the plating peeling off the metal, and to prevent this the aim is to obtain as thin a plating as possible.  This very thin plating tends to be quite bright and shiny.

At some later date, somewhere between 1917 and say 1920, Meccano would probably have upgraded its nickel plating facilities.  There was substantial growth in the company, and by the end of the decade anyone who was anyone was using Watts' new process because of its improved quality and efficiency.  The resulting plating would have been thicker, and therefore duller, than previous finishes.  This process continued up to the end of 'normal' nickel-plated Meccano at the end of the 20's. 

Later on, many other developments were made to the process, including the regular addition of organic compounds to control and brighten the finish of the nickel plating.  Those parts that were still nickel-plated gradually became brighter and had better quality plating, right through to the 50's and 60's when the process was dropped in favour of zinc plating.

Nowadays, almost all nickel plating is done as a base for chrome plating.  Chromium plate is in fact transparent, and the shiny mirror finish of 'chrome-plated' metal comes from a high quality, thick coating of nickel plate that is immediately chrome-plated to protect the surface.  As a result, development in nickel plating has been to provide a thicker and brigher finish, completely unlike the original finish of pre-1930's Meccano parts.

For this reason, it can be difficult to restore early Meccano parts.  You really need to find a nickel plater who understands the difference and (more importantly) is happy to set up a dull nickel bath according to the old-fashioned recipe.  It won't be much use to him for any other purpose than your job, and for this reason you might find that dull nickel plating is simply uneconomical.  But if you do find success in this, please come back and tell us!

Back to Graham to summarise this for us:

I fully agree with this, except that I should like to propose that very early nickel parts, prior to Meccano's use of the Watts process, were noticeably brighter.  In my collection, parts that can be dated with certainty prior to 1919 are generally much brighter than later ones.  There is some variation, as the processes are very sensitive to ambient temperature, concentrations of solutions, and the presence of impurities that have not been filtered out.

Should I replate nickel parts?

This is going to have to be a question for you to answer.  If you replate old nickel parts by modern process, you will not get anything approaching an appropriate finish.  However, if you like the shiny finish then you will be happy.  You may be able to find a plater who will ease off the brightening agents and be able to give you a finish similar to post-war nickel plate -- and this will be a great improvement to even quite badly affected parts.  If you're very lucky you'll find someone knowlegeable and prepared to attempt the old dull nickel finish, but it won't be easy.

Having said that, nickel plating can turn rusty old bits into super parts for building purposes, and I personally replate all small brackets and nickel bits and pieces.  But I draw the line at old strips and plates.  The price of plating is fairly high, and all you can do is turn the parts into historically irrelevant parts.  If the finish is not perfect on the part you send in, then the imperfections will be amplified by the mirror finish of the plating.  However, the strangely pitted rack strip shown above is still far better than the dark brown rusted example I started with.