home - Part 1: Photoless photoetching
This article is not exactly about photoetching. Perhaps I
should call it simply "etching at home". I won´t write a
dissertation here about photoetching or PE parts. You know what it is
all about. After all, we spend a lot of money buying those marvelous
details, and it is generally a well invested money (well, not always),
since it adds a lot to our models. But what to do when we can´t
find a PE set that suits our needs? Sure, we can scratchbuild them in
plastic, metal or whatever. But, as always in scratchbuilding, we are
limited to what we can see and our tools can reach. This limitation is
somehow present in resin parts, too (a professional master is doing the
hard work for you, right?). That´s what makes PE parts a category
of them own: the subtlety of the details - in size and complexity. And
this also why not everything can be made by photoetching, remember
What about making our own PE parts? Sounds intimidating, eh? It
should, because photoetching is indeed a difficult process,
particularly if you never tried it before. And dangerous too, as you
will work with corrosive substances.
What you mean by photoless?In a nutshell: Experienced modelers know that photoetching involves chemical erosion (or chemical milling, or chemical etching, or whatever...) of appropriate materials (brass and nickel silver, typically). This means that the metal is immersed in a corrosive solution, which will actually etch the metal. But the etching must occur only where it is wanted. In general, the metal sheet is covered by a photo-sensitive varnish. Then a (negative or positive, depending on the varnish type) film with a precise drawing of the part is laid on the sheet, which is exposed to a UV light source. The light will not traverse through the black areas of the film, and so the corresponding varnished areas won´t be "cured". A bath in caustic soda solution will "develop" the varnish layer, that is, it will remove the varnish from all areas not exposed to light. Now the sheet can be immersed in acid to be etched, but the acid won´t attack the areas protected by the varnish. If the part is etched for a time long enough, the acid will remove the material all the way through its thickness. If the process is halted before that, the result is a sheet partially etched, with recessed details. The procedure can be applied to both sides of the metal sheet.
Developing the imageWe want to avoid the photographic part of the process as this is our first etching section. Therefore, we need something to protect the areas that won´t be etched. The answer is probably on your workbench right now: Future floor wax. In fact, most paints will work. I prefer clear acrylics because it will resist better to the acid.
Now start drawing what you don´t
want to etch: your artwork will be the raised areas of the part to
be etched. You will need the aid of some old fashion drafting tools,
templates, but your scribing templates can be used as well. When using
templates, remember to stick small pieces of tape on the bottom side to
create a gap between the template and the drafting surface (our brass
in this case). This simple action (a draftsman old trick) will prevent the wet traces from being blurred by the template.
Use the drafting pens to draw the contour of the areas to be protected, and fill the inner areas with a liberal amount Future. In general, I use the 0.2 mm pen to draw the edges and the 0.6 mm pen for filling. Sometimes it is just a matter of using the right pen - no filling necessary. Rivets can be made with "dots" of Future. I made a fictitious drawing using some basic shapes for this example. Let it dry completely. Close exposure to a bulb will dry it well in a matter of minutes. I don´t recommend the use of a hair drier, as it can make the wet Future bleed. Here´s how it looks so far:
that everything is set, let´s start etching our workpiece. I like
to use ferric chloride, because it
is not particularly dangerous as other solutions are. It is the
slowest of the common etching solutions, but you can accelerate the
process by preheating it. If you want to know more about how it works, take a
look here. It is a mild solution, but of course still a corrosive
chemical, and must be used with care and protection (use coverall,
rubber gloves and goggles). Although not absorbed through the skin, it
may eat your clothes fiercely. By the way, do yourself a favor
don´t buy the solid stuff (which must be dissolved in water - a
mess). Get the liquid one, ready for use. For your references, here´s a Material
Data Sheet for a typical ferric chloride solution.
Another approachI know not many of us are talented for drafting. As another example, let´s try a different approach. This variation of the method avoid the drafting part. We will use dry transfers as our protective layer. The method is particularly attractive to etch bezels, handles, plates and other small details. In the case, I need to etch a couple of cross-shaped handles for my current Me-262 project. Fortunately, I found an old Letraset font whose plus sign was exactly the shape and size needed. So I burnished some of them on a small piece of brass, prepared and cleaned as before.