Matt Black Coal Paint

I was looking for a high temperature paint for my small vertical boiler. It need to be suitable for the firebox and hence work at high temperatures. I wandered into my small local hardware store and saw matt black coal paint. It was just £3.99, worth a go if nothing else. It wasn’t until after I had used it that I realised what it was actually for.

spray matt black coal paint

How did I not just read the title that was on the can and put two and two together?

I thought “coal paint” was just a way of describing the black colour and finish…

This is actually paint designed to be sprayed onto fake coals and so make them look once again like real coal. Wow, there really is something for everything and anything is possible.

However, before putting two and two together. I had tried this paint on the firebox of my small vertical boiler.

small vertical boiler firebox

The small vertical boiler firebox was made from thin sheet mild steel.

The sides were riveted together and the top and base were silver soldered to the the side panel construction. The result was a solid construction.

The image here shows it after I had treated it with “gun blue”. My first attempt at creating the matt black finish. However, as you can see this finish tends to rust. This is even worse as the methylated spirit burns and releases a lot of water that condenses on the steel.

Hence I needed to paint the firebox.

matt black coal painted firebox
Just one coat of the coal paint and the finish looks ok.

Coal Paint made by Rapide Products

spray paint protective cap

I noted online that lots of people comment that this spray paint doesn’t work very well. The can stops spraying after just a small area has been coated.

Well, there is a plastic washer under the spray nozzle designed to inhibit the nozzle releasing spray. However, it releases enough to give a splatter of paint.

Read the blinking Instructions.

How many times do you hear this as an apprentice?

It even says on the edge of the can that you need to read the instructions. One of the first items is to remove this plastic washer.

This particular matt black coal paint is supplied by Rapide Products (

This is actually a coal paint, designed to be applied to fake coals. However, if you read around the internet on similar products it does specify that they can also be used on metal flues, grates and the surface of a stove itself. After applying 2 coats to the firebox I used it and heated the boiler to it’s operating point. To do this I used an open flame in the firebox, hence it got very hot indeed. After cooling the matt finish actually looks better.

The conclusion is that this paint works very well on metal and very well on areas that will see extreme heat. Just be careful and read the instructions….

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