Hi everyone,
So I was wondering if anyone could help me on some rust blueing troubles.

Basically Im struggling to get the deep jet black colour and currently only getting a light black/grey. Ive read Angiers book and decided to try a few formulas out but with pretty much the same results. Im getting no streaks or blotches, so happy with my degreasing and application of the solution but just the colour.

Ive tried C.17 swiss black (beutel), C.19 ferrobronze and C.10 Twist barrels K Birmingham black. The first rusting is a good coat of brown/red rust and takes 4ish hours in a sweat box of 40C and 80% humidity to form. I then boil for 15mins in distilled water to convert the rust and card off. This gives a light grey colour. The second rust coating takes a little longer and not as thick but you can see its there. I then repeat the process in boiling and carding and get a darker grey. The third coating then takes a good 18 hours plus to get a little bit of rust and after boiling hardly changes the colour. The forth coating barely puts any rust on the part at all, after 24hours in a sweat box. I believe this is where its going wrong in obtaining a real deep black and was wondering if anybody else has had these problems on the 4th application.

The only things I can think of are:

The test pieces Im trying it on first, before my own William Powell shotgun barrels are walther rifle barrel off cuts and may be high in chrome and nickel making the solutions ineffective. However I know people in the UK can rust black walther barrels with amazing results so not sure about this one.

Or maybe im getting the boiling wrong, maybe too hot or for too long, causing the metal to reject the next application (trying 5 mins boiling time as I write this now)

Was also thinking of increasing the solution concentration by adding less water than what Angier quotes to see if this will get me better rust coats on the 3rd and 4th application.

Apart from that Im out of ideas and any help from the more experienced rust blue ers on this forum will be much appreciated.