[CR]Reproducing a head badge (Long..)

(Example: Bike Shops)

Date: Fri, 7 Nov 2008 17:16:08 -0800 (PST)
From: "Norris Lockley" <norris.lockley@yahoo.com>
To: classicrendezvous@bikelist.org
Subject: [CR]Reproducing a head badge (Long..)


I knew last night when I was hastily rattling off my initial response to th is problem of Harvey's that I had forgotten something..something simple and not expensive and not requiring sophisticated tools, such as die-sinking, which would be OK for runs of 10,000, or so badges.

I would like to add to Gabriels comments on my suggestions as he has elabor ated very fully on a couple of them.

The method that I called electro-deposition is also known as Gabriel pointe d out, as electro-forming. During the process, normally done in a vat or ta nk in a manner similar to chrome plating, the pattern ie the mould in which you wish to deposit or form your finished product is placed in the vat wit h the appropriate solution, and electrodes of the material you wish to depo sit on the mould are placed in the tank at strategic places, depending on t he size and shape of the form to be made. I am not an industrial chemist so I am uncertain of the terminology, but have often seen the process car ried on both small and very large objects. Presumably an electric current i s passed through the solution, and the pattern and the electrodes become th e anode and the cahtode, or should that be the positive and the negative. A nyway you get the idea, I'm sure.

CORIMA, the maker of those exotic carbon wheels,  and wonderful carbon fi bre track frames eg Chris Boardman's  World  Hour Record machine, is one of Europe's leading exponents of this technology, as an ancillary servi ce to their activity with composites. Originally pattern-makers, the compan y diversified into non-wood patterns. They still produce the wood patterns from which a composite pattern is made. This tool, is used to form a  fem ale nickel and copper tool  - copper first for thickness and lower cost a nd then a thin layer of nickel for hardness and durability -that is in turn used in the moulding, possibly by slush moulding or sprayed moulding proce sses of plastic dashboards and bumpers in the car industry. If you look c losely at the leather-look finish on the plastic surface of your car's da shboard, you will realise just how fine is the detail that can be obtaine d by this electroÞposition process.  The moulding tools for most of t he domestic resin or composite kitchens sinks are made by this process . Abou t thirty years ago I bought a home hobby kit that worked on this principle that enabled little pieces of jewellery to be made

Gabriel also mentioned rubber moulding compounds from which moulds can be m ade, when an original tool ie a cast headbadge is available. These media ar e available in the UK under names such a Vinamould and Vinagel..and are use d often in secondary school metal workshops for making small castings.

The process above assumes that the finished badge will be a casting. Howeve r if the original is a low relief pressing or industrial etching then the re is a simple way to reproduce that original. Photo etching has been menti oned and Gabriel suggested various resists that he has used. However many a rtist etchers and home hobby etchers can achive very good results using the time honoured process of painting the design on to the parent metal with w hat is known as a resist varnish. This is simply a type of black varnish th at will adhere to the parent metal and which will resist the corrosive acti on of the acid during the etching process ie it will resist being lifted of f or eaten wawy. Most good art supplies/craft shops will be able to supply small bottles of this stuff.otherwise it can be made easily in the home usi ng benzine to dissolve flakes of asphalt/tar until a reasonable varnish-lik e viscocity is obtained.. The design to be etched is drawn or transferred on to the parent metal, remembering to black out with the varn ish, those areas that will be proud, or stick up in relief on the parent me tal. The hollows etched away can be either enamelled..a relatively simple p rocess that can be done at home with simple equipment, even a small butane flame, or with a hobby kit from your local craft shop...or filled will pa int.

One good way to get an accurate likeness of an original headbadge is, assum ing you can get your hands on an original, to take a brass-rubbing of it wi th a soft black lead pencil and tracing paper. This is the same process as that used by folk who like to take rubbings of inscriptions on grave stones or commemorative plaques of all types.

The soft rubbing of the pencil over the paper stretched over the badge wi ll highlight the edges of the relief on the surface of the paper..and a sor t of tracing, andoutline of the design can be obtained. At this point fra mebuilders should stop reading. The technique that I have outlined above--- puny Eh ? - is often used by framebuilders when they wish to copy the curly lugs of other builders such as Hetchins, EG Bates, etc etc..So next time  at the tea-stop cafe you see a fellow cyclist acting suspiciously toward s the headlugs of your fany lugged Claud Butler, it's not envy..its indus trial fraud. The resulting tracings can then be stuck to the lug blank, or transferred in other ways with carbon paper.

As mentioned this tracing can be stuck to the parent headbadge metal with a layer of good carbon paper underneath. The design is then traced over with a sharp A4 pencil or similar implement. When all the outine of the design has been traced the original rubbing plus the carbon paper is carefully lif ted from the brass and...hey Presto..you have  design that can be painted with acid resist..and then dunked in the acid tank. As  Gabriel said, ni tric acid will work well as a mordant on brass, copper, pinchbeck metal/gil ding metal, or nickel silver..as will ferric oxide. It's a long time sinc e I last etched any  sterling silver, but I seem to remember using sulphu ric acid on that metal. On aluminium and pewter I used hydrochloric acid.

Obviously there are many safety measures that should be observed when mixin g acids..and when the etching process is in full swing in the acid bath eg etching with nitric acid gives rise to a pungent, noxious and acrid sme ll from  the bubbles of gas produced by the process. Using ferric oxide ( or some proprietary etching mordants supplied to the home craft trade) doe s not produce this gas. Ferric oxide also has other advantages. Whereas nit ric acid etches very quickly and has a tendency to produce slightly rougher fields ie the parts of metal left in low relief by the removal of the meta l, (although a weaker solution of acid  and water would slow this down) , ferric oxide has a slower action and produces a smoother and more detaile d finish. Additionally nitric acid  necessitates the metal being etched t o be placed in the acid bath with the design upwards, so that the bubbles o f gas that form can be released upwards. During this process it is necessary to regularly brush the surface of the work-piece with a feather or some such device to brush off those bubbles that do not rise of their ow n accord. Where bubles are not removed and airlocks form,  the acid canno t attack the metal and etch it. On the other hand, ferric chloride needs th e parent meat to be placed design side down. No bubbles are formed, and the etched away residues fall away by gravity, leaving a far more regular fini sh, needing less supervision. Once a satisfactory depth of etching has been produced, the metal is remove d from the acid, with non-ferrous tweezers, and washed off with water. Then it is up to you what you do next...polish, paint enamel... It might be useful; to, pint out that to obtain the best finish, it would b e advisable to very slightly ..and I mean very slightly, abraid the surface on  to which the tracing is to be made and the varnish resist applied, w ith some very fine steel wool or extremely fine  wet-and dry. This would produce a no-glossy, slightly textured surface on to which both the traced lines and the resist woukld adhere better.. If you wish to try a simple l ittle experiment to test your skill, obtain a piece of brass or copper, and go to your local graphic design shop and get a few of those vinyl self adh esive letters that were know by names such as LETRASET. Try some small lett ers too..not just capitals. Prepare the metal and the acid bath..then apply one or more letters to the surface of the meatl ie in this case the plasti c letter is acting as the resist varnish..make sure it/they are well adheri ng...place the metal in the acid...follow the instructions above... Some time later...you will have a finished etched headbadhge with the lett ers of your choice. Now borrow a tube of nail varnish from your wife's dres sing table, apply the varnish,( acetone based) withn the brush provided  to the etched portions - the basse fieds - of your headbadge...and you have, in a sense, an enamelled headbadge.

I can now imagine just what a lot of you guys will be asking santa to put i n your Christmas stockings..stuff the likes of which your wives would never think of. Gone the expensive bike parts for Christmas ! I think I will jus t have one of those homecraft etching kits from the Hobby shop this year, l ove..thought it would be cheaper for you to buy this year than the Campag c hainset, particularly now we have helped to bail out the baks with ourn tax es, and it would help the country's economy during the recession if we bo ught uSA produced products.

There is always one last thing..my intentional oversight. Before anyone who wants tio try their hand at this fascinating craft  emails me to ask abo ut the omission that I have made, let me spare you the trouble. When etchin g with nitric acid, the metal being etched should be place din the tank/vat with the design faing upwards. This means that the metal can rest on the b ottom of the tank, for instance a Pyrex or earthenware dish. On the other h and when using ferric oxide solution the metal has to be place in face down wards, which means that if it is placed on the bottom of the bath, the mord ant will not be able to get to it - therefoe no etching. All you have to do is to get some lengths of brass or copper or nickel wire long enough to sp an the tank, with some over. Bend the wire into a shallow flat-bottomed U s hape which will rest in the etching liquid, and then make a hook at each en d of both wires so that they will hook over the edges of the dish/tank. The metal to be etched is placed, face-downwards, on this wire support.

Don't think I have left anything out....

Norris Lockley, Settle Uk