Archive for Ideas

Tiny Signs

Abingdon Platform SignAfter much nagging and bullying from you know who, I spent much of the weekend and a little of yesterday evening trying out different tequniques for painting the etched sign (see previous article).

Initially, Ivan and I had got together on Thursday evening for a good old chin wag and “planning” session that rapidly turned into a making, testing and experimenting session.  We started by cleaning the least successful platform “Abingdon”  sign with a glassfibre pencil.  After carefully cutting it from the fret and filing of the burrs, we soldered it to a couple of rail posts and glued a piece of plasticard to the back to help disguise the holes.  Ivan dug out some black primer spray paint and after five minutes dancing around the garden playing samba rythms (rattling the can) he sprayed the sign matt primer black.

For the lettering, we tried the suggestion of using a roller to just add paint to the raised parts of the sign but unfortunately this was disasterously unsuccessful (though may work with some of the smaller signs).  After re-applying the primer, I used a small brush to carefully paint in the lettering.  It takes a very steady hand and a lot of patience to achieve good results this way and despite using Ivan’s magnifying glasses, the end result was looking very ragged with a lot of accidental slips needing to be fixed with the primer.

To the River & Salters SteamersGW NoticeOver the weekend, I was able to get hold of an even smaller brush (OOO) and clean up some of the edges and cover over some of the slips.  A quick rub with the glass fibre pen helped to take the shine off the lettering and a brush over with weaathering powders toned down the white and gave the whole sign an aged look.

With the smaller signs, I used a slightly different method.  After painting in the background base colour with black paint, I used what is commonly called a dry-brush technique (I think !?).  Goods Office SignI loaded a flat and relatively wide brush with the white paint and then carefully wiped it on a piece of scrap paper until only a small amount of paint remained on the brush.  This was then very lightly stoked across the signs so that only the highest parts of the lettering picked up the paint.  I repeated this several times until there was enough paint built up on the letters.  This method seems to have been very successful, particularly on the GW notice that will be fixed to the side of the goods office.  (Incidentally, if you take a look at in the “Martin Smith” collection of photographs on our www.abingdonbranch.co.uk website, there is an excellent image of the original sign in glorious technicolour.)

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The Acid Test (results)

Disappointing results

Disappointing results

Having set up the acid bath, making sure to follow all the necessary safety precautions we got down to the all important preparation of the brass in readiness for ironing on the resist which had previously been printed, using a laser printer, onto the special toner-transfer paper.

The first fret that we tried was a “Crane Wheel” fret.  The brass was given a good clean with wire wool and then wiped with methylated spirit to remove any remaining grease or grime.  The piece of brass was slipped into the pocket made by folding the toner-transfer paper corresponding to the registration marks included on the print and stapled in place.  It was then ironed on both sides for about 5 minutes in the hope that the toner would transfer sufficiently to provide the necessary “resist” to prevent the required area being etched by the acid.

After about 15-20 minutes in the acid bath (regularly checking progress), the fret was removed and given a thorough wash to remove all traces of acid.  As can be seen form the photo, the results were rather poor and disappointing.

Still poor results but showing promise

More care = better results

 The next fret to get the acid treatment was the Abingdon Signs fret.  Again the brass was prepared and the toner ironed on.  This time it was realised that tiny specs of dust were trapping air between the brass and the toner sheet, preventing adhesion in those areas.  As you can see from the photo to the left, these caused holes to be etched through the sheet where they weren’t intended.  It was also realized that the areas with no toner also trapped air which expanded with the heat of the iron, forcing the toner away from the brass along the edges and causing jagged edges to some of the signs.

With the next attempt at the Abingdon signs, we took a lot more time and care, firstly in making sure the toner sheet was clearer of dust by giving it a quick blow and secondly by piercing every air bubble trapped beneath the toner sheet.

More care = better results

Success!

On the photo to the right, you can see that there are fewer holes and the edges of the signs are cleaner, straighter and smoother.

By printing the sheets closer to the time that they will be used (in this case they were printed about 3 weeks before use) and by taking more care in keeping them clean and free of dust, we should be able to acheive even clearer etches in the future.

Tiny Sign!

Tiny Sign!

Cleaned up with a glass fibre brush you can see the level of detail that has been achieved even in this first attempt at the technique.  Considering that the goods shed sign is only 10mm across and the lettering not much more than 0.5mm tall, you can see from the following photos that the text is almost readable.  Certainly clear enough for it’s intended use and viewing distance. 

  

Success!

Success!

You can see that the slightly larger lettering on the Goods Office sign is perfectly clear and usable.

Whilst it’s true that at this size the signs don’t really need to be 3 dimensional and excellent results can be achieved with a standard printer, I don’t think that would be anything like as satisfying or as much fun!

The next problem to overcome is how to successfully paint the signs without obliterating all our effort but I’ll leave that for a future blog … watch this space! 

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The Acid Test (experiments in etching brass)

Drawings for the "resist"

Drawings for the brass frets (reversed so they apear correctly on the final etch)

After looking for parts suitable for several of the Abingdon structures and failing miserably to fabricate them in other ways, we are experimenting in etching them in brass.

The process, also known as “chemical milling”, uses acid to “eat” away unwanted parts of a sheet of brass to leave the required shape. In order to control the bits that are removed and what is left, a “resist” is applied to the brass in the places to be preserved which shields it from the acid.

Once the acid has done it’s work, you will be left (or so the theory goes) with an etched brass fret. This is effectively the same process that is used to produce the brass kits with which many of you will be familiar (though the commercial process is somewhat more controlled and sophisticated).

As luck would have it, the same process is widely used in electronics to produce circuit boards from copper clad board (PCB) and all the necessary kit (brass excluded) is available from the likes of “Maplins”.

Doug, already having all of this as well as experience in etching his own circuit boards has kindly agreed to try the process with the prepared drawings and brass.
If it is successful, I will describe the process in much more detail.

Watch this space!

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