Bow pen lining problems

[robmort]

I'm trying to use a bow pen for the lining of boiler bands on a 2.5" scale model by angling the pen along the edge of the band. I'm using Humbrol enamels straight from the tin. The pen is sharp. It gives good results with smooth straight lines when used on the edges of test pieces of brass plate, as shown on the left.

But when used along the painted bands (on the right) it gives a very lumpy line. The line starts well when first put on but the paint spreads sideways unevenly shortly afterwards. Any ideas what is going wrong?

IMG_2031 by rob1524

[chris vine]

Hi Rob,

I haven't ever seen this problem, but here are a couple of thoughts:

1, is the paint going on so thick that it is just overflowing onto the black?
2, is the humbrol paint compatible with the black paint? What happens if you apply a line of white to the black with a small brush, just as an experiment?
3, is the black paint fully dry?

I only ask these last two as you seem to be having some success onto the brass sheet, IE where there isn't any other paint involved!!

Chris.

[simon6200]

I did mine by first painting them black, then masking the middle and painting the white edges. So much easier. I used Tamiya tape which comes in various widths.

[robmort]

Chris,

the black was fully hardened after a few weeks and is also Humbrol enamel. Using a brush for white shows no problem. The white and the pen was the same on both the brass and the bands, so wouldn't expect a difference.

The only reason I can think of is that the black surface has somehow a low surface tension in some places. I'll do some more experiments with painted edges, but nothing is ever as easy as it looks!

Simon,

How do you ensure the masking tape is the right width and gives a thin uniform edge when the line width is only about 30 thou (in my case) and the band is only 1/8" wide?

[oldnorton]

Find out first if the surface is at fault. It might have picked up a contamination that has reduced surface tension perhaps? Maybe wiped with a cloth used for polish? Try lining on another old painted surface that you can pre-clean with detergent.

Is the white paint fully stirred? Try an alternative to that tin of Humbrol. I use "1 Shot Lettering Enamel" which is old school sign writers paint. I wonder if the Humbrol paints are increasingly formulated to be 'safe' for modellers.

Norm

[simon6200]

Mine was wider, 3/16 I think, probably used 3 mm tape. If you used 2 mm you wouldn’t get 30 thou white.

[chris vine]

On the masking idea: you could cover the whole band with tape and the cut off the edges. A sharp bow pen might just be able to score the tape so you can pull the edges away to leave a perfectly set mask in the middle…
Chris