Brass Etching

There are a few different ways to do brass etching, but having learnt how to do this with a really simple method I just had to share it. The real drive for this is to produce the brass lettering on the smokebox door of the Burrell traction engine. You will need:

• Laser printer – or access to a photocopier
• Inkjet glossy photo paper
• Brass sheet
• Ferric Chloride
• Plastic Tub

So, here are the simple steps:

1. Create image of the areas to be protected – these will be the black printed areas
2. Reverse the image
3. Print the image with a laser printer onto inkjet photo print glossy paper
4. Clean the brass sheet
5. Iron the printed image onto the brass
6. Soak the brass and paper in warm soapy water
7. Etch the brass face down in ferric chloride
8. Wash the brass in warm soapy water
9. Carefully sand the black print from the brass

1. Create the Image

I created the main image in Microsoft Powerpoint, but any application will work. Just be careful with the crispness of any edges and trying printing the image out at slightly different sizes onto plain paper. This way you can scale the image in the application to the final result that you require.

For the best image quality and flexibility in the design then Inkscape is probably the best application. It does take some effort to learn though.

2. Reverse the Image

The image is going to be pressed onto the brass and hence needs to be reversed.

Just be careful again on the scaling when you reverse the image left to right. Also, I reversed the image by turning the powerpoint objects into an image and then dragging it left to right. In powerpoint this reverses the image.

However, note that when you turn an object into a bitmap in powerpoint it can generate some spare pixels.

3. Print image onto Inkjet Photo Paper

It does feel strange laser printing onto inkjet paper, but the reason is the inkjet glossy photo paper doesn’t absorb the laser ink.

The ink remains as a layer of plastic on top of the shiny plastic surface of the paper.

Note: the photo paper tends to be a heavyweight paper and I found that it didn’t easily get picked up out of the paper tray. I ended up rolling the input edge to soften the paper, allowing it to more easily run around the rolls.

The best paper I have used to date is WHSmith 150 GSM Glossy Inkjet – this is a cheap everyday paper and the lightweight appears to make it easily peel off. This lightweight paper feeds through the laser jet printer easier.

4. Clean the brass sheet

Clean the surface of the brass, firstly with a fine sandpaper and then with wire wool. I then used a small amount of methylated spirits on a piece of clean cloth to remove any grease from the brass plate.

Some say use acetone to remove any trace of grease. I wash the part with normal washing up liquid and then once thoroughly degreased I then clean with acetone.

Finally I washed the brass sheet with a very small amount of detergent and warm water. Dry the brass on a clean cloth.

5. Iron the image onto the Brass sheet

Cut out the inkjet paper image and place it face down onto the brass plate.

Set the iron (by this I mean the household clothes iron) to just below the highest heat setting. Then with a sheet of paper between the iron and the back of the image you have created carefully heat the paper. I held the iron in place for 10-30s.

Whilst it is all hot I used a printers roller to firmly push the print onto the brass sheet. This helps ensure all of the plastic ink has stuck to the brass sheet before you remove the paper backing.

6. Remove the paper backing

If the paper is thick you will probably need to soak it to be able to remove it cleanly. If you use a lighter weight paper eg 150gsm then it should carefully peal off leaving the ink attached to the plate.

7. Etch the Brass in Ferric Chloride

You can buy 0.5 litres of iron chloride on ebay for a reasonable price. Note that it will last quite a long time and you can keep reusing it.

Hang the part to be etched face down in a plastic container. Then gently pour the ferric chloride in until it covers the part. You can use gaffer tape on the back of the part to resist the etching.

I placed the part in the ferric chloride on a cold day and so left the parts for around 2 hours to get an etch depth of around 0.3 to 0.4mm

You can heat the ferric chloride bath to improve the speed of etching. I place the ferric chloride bottle into a bowl of hot water. The optimum appears to be around 70°C, but I find that ~35-45°C is fine. You just might need to extend the time depending on temperature.

Adding air to the tank using a fish tank air system will improve circulation and the consistency of the etching.

Ferric Chloride or Iron III Chloride reacts with the copper in brass in a 2 stage process:

1. FeCl₃ + Cu -> FeCl₂ + CuCl
2. FeCl₃ + CuCl -> FeCl₂ + CuCl₂

I made a plastic etching tank and have added a bubble chamber to aid the flow of the ferric chloride. This improves the mixing and hence quality.

Plans for the etching tank are available on the glue-it.com website.

8. Wash the Brass after Etching

The etched part removed from the ferric chloride. Be very careful to wear gloves and eye protection when handling ferric chloride.

Remove the excess ferric chloride with a cloth and then wash the part thoroughly with warm soapy water.

9. Sand, Polish the Brass

Finally you can carefully sand, polish or paint the part.

This is a simple brass etching method and you can now effectively etch anything that you can print.

Further Reading

1. Edinburgh Etch – an improved ferric chloride based chemical that uses an addition of citric acid. Full details of the mix and improvements to the process are given on this page.
2. Von Industrial – Tom Utley has etching down to a fine art and you can get a plaque etched for a special project at a very reasonable price.

Burrell Engine Nameplate

The brass nameplate for the 1/20th scale Burrell traction engine. The capital letters are just 1.4mm high.

Brass Etched Mantlepiece Clock

The 1/12th scale antique shop made by Roy Taylor includes two working clocks. The faces of the clocks were etched using a photographic technique in the home workshop.