I have some bright red paint and some black, same manufacturer: I want a dark red colour. Will mixing a bit of black darken the red or produce a bleeding mess?
So long as they are the same kind of paint it will be fine. Add a little at a time until you get the colour you want (or a colour that is acceptable if you're not to worried about it!)
Be sure to mix the paint really well. I salvage old whisks from redundant food mixers for this purpose. Fit them into an electric screwdriver or drill, and it makes a tedious task much quicker.
Also very useful for mixing antifouling - much more eficient than using a stick!
Don't know much about paints outside of the art scene but I assume that is much the same. In which case the more pigments you mix together the more chance there is of getting a muddy result and in any event the cleanliness of the colour is diminished as you use more pigments. The red paint you have is obviously not muddy, nor is the black, but the red will almost certainly not be a single pigment paint and if the black you add is also not a single pigment paint then there will be a risk of getting a muddy result - probably as reported by Chippie.
As has been said, 'cause you don't know the pigments in either of the paints the only way is to try mixing a little and seeing if it works. If the result is not muddy you should have ended up with a darker red but its saturation will be reduced (not so much "redness" present) as you have diluted it with the black as well as greying it so the result may still not be what you are looking for.
If you love polishing then apply a red paint, that's what you will be doing a lot of to maintain it; red is one of the more difficult colours to maintain on a boat as UV effects most brands.
Avagoodweekend..........
<hr width=100% size=1> Old Salt Oz /forums/images/icons/cool.gif Growing old is unavoidable. However, growing up is still optional.
Intelligence and age cannot replace experience...thanks to all for your advice (on the basis of which I've decided to paint it.....white). Incidentally, it is a box that holds 2 Camping Gaz cylinders and lives in the (open) cockpit.
If you havent already bought the paint, I recommend a water based enamel. I used Dulux aquanamel white on my cabin and cockpit and find it is hardwearing and resists oxidising a great deal more than the oilbased one I used last time. A small area like a box is an ideal thing to try it out on for yourself.