Sorry for the noob question. Have been trying to learn zbrush over mudbox these days.
Occasionally I notice these dark brush or display artifacts in my sculpt. Can any one explain what the cause is? Is it related to overlapping faces, normals or the rear face coming through the front? Doesnt seem to affect the model once I export.
Id love to know the cause, perhaps my workflow is a little off.
Appreciate any advice 
Thanks.
It looks like the areas are slightly masked but I can be wrong I’m also new at Zbrush but just check if its a mask
That’s either masking or it could be color (black) being painted on the model. To clear the masking just hold ctrl and drag, the entire drag motion has to be done off the model. If that doesn’t clear it then it’s probably paint information.
Thanks for the reply MentalFrog, its definitely not masking. Not sure if ive ‘painted’ on the surface indirectly. I dont see how. I find this type of artifact appears mostly when I use the smooth brush. Can you disable painting on the surface just in case?
Any other ideas?
Sometimes when a brush is changed it will have RGB enabled by default, smooth brush I believe is one of them. Probably accidental.
To clear the color select the standard brush and make sure RGB is selected (not MRGB). Then make sure the current color is white. Click on Color > Fill Object. This will fill the object with the current color. Make sure you only do this if you don’t have polypaint information on the model that you don’t want to lose. If you have MRGB selected it will fill the object with the current color and the current material. To erase the material information select M (or MRGB if you want to do color and material) and then select the Flat Color material in the Standard Materials. Then click Color > Fill Object. Your object should turn completely white and flat. Now when you switch the current material back to your sculpting material (default is the red wax) then the model should switch back.
Thanks for the replies and advice.
Ill try/look out for this.
D