Wikipedia:Reference desk/Archives/Science/2022 April 11

= April 11 =

Electrotyping of mid-19th century
Even after I looked up electrotyping I still don't get it. Can someone explain what it is in simple layman's terms. I'm reading a biography from a 1915 book and it says, He invented the art of electrotyping in copper, wood-cuts and type such as are used today. In simple terms what does this mean? The book goes on to say, In 1846 he electrotyped in copper the arm of a child. What exactly did this inventor do here?--Doug Coldwell (talk) 10:50, 11 April 2022 (UTC)
 * It's the same as electroplating, basically, just using a shaped mold which gets filled in with the material being plated (typed in this case, I guess). The way it works is that you have an electrically conductive mold (the cathode), and some kind of metal ions in solution, along with an anode made of the metal whose ions are in the solution, which you are going to plate.  If you drive an electric current through the solution, the metal ions pick up the electrons at the cathode, and become reduced to the native metal; at the same time, electrons are taken from the anode, oxidizing the metal to provide more ions to the solution.  So long as an electromotive force (i.e. voltage) is correctly applied, the process will continue until the anode runs out.  -- Jayron 32 11:17, 11 April 2022 (UTC)
 * To respond to your italicised sentence specifically. First a negative mould is made of the object, whether it be an child's arm or more commonly a wood-cut.  The mould can be made of a low-temperature setting substance such as plaster of Paris.  The mould is coated with a very thin layer of a conductive material, often graphite.  From memory (but unfortunately without citations) the conductive surface can be applied directly to the original and can then be taken up by the mould.  Then, as  explains copper is deposited onto this layer creating a negative of a negative = a positive!  Once a sufficient layer has been built up for the particular application, it can be parted from the mould and a backing applied as required. Martin of Sheffield (talk) 11:35, 11 April 2022 (UTC)
 * There was also a papier mache version of the process. Here's a book about it: Stereotyping and electrotyping. ...In fact there are plenty of other books linked to at the foot of the article. Card Zero  (talk) 12:08, 11 April 2022 (UTC)
 * Be careful with that book. The first part contrasts and compares the plaster and papier maché methods, but that is for stereotyping a quite different process.  Starting on page 112 it only mentions wax as the mould material for electotyping. Martin of Sheffield (talk) 13:53, 11 April 2022 (UTC)
 * Oh, dammit. Perhaps I'm being confidently wrong. Card Zero  (talk) 15:49, 11 April 2022 (UTC)