[Nightfirecat]

I'm trying to define a brush in photoshop--of valentine's brushes, specifically, and whenever I do one, especially when it has gradients or multiple colors, it is transparent... Is there any reason why?

When I made the original, it wasn't transparent--it was opaque, completely...

[Raised Grain]

The opacity slider may be set to low.

[Nightfirecat]

Originally Posted by Raised Grain

The opacity slider may be set to low.

Hmm... Where would that be? Just on the brush preset, or is there some sort of opacity setting you use when defining the brush?

I made sure that all the opacities were set to 100%...

[Raised Grain]

The one I use is in the menu bar on top. It has a slider to define the opacity. Not sure if this will work for you. Also on the far right of that menu bar is a button for brush dynamics. Not sure what its function is, never used it but it has three adjustments, mine are all set for OFF.

[ProHermit]

Apart from the opacity being correct, in the same box as this, make sure the brush option is set to normal and not to screen, overlay, soft light, colour dodge, etc, etc, etc. This all depends how you are using your brush or air-brush in relation to the back ground image, layers, etc. Try different options until you see which one works and why.

[Raised Grain]

ProHermit:
Do you know how the "Brush dynamics" are used?

[ProHermit]

As a general rule, yes. It's all about experimenting until you get the desired effect.