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