Was mainly setting up Lightcap, but adding texture at the time. Not sure what’s gone wrong but strange materials disappearance, however mostly somehow got most back. All my Lightcap & lights have gone blank and black, even though there is still one light found nowhere in settings.
Is this a bug ?
I assume at the moment it’s my gfx card due to endless redraw errors with other 3D apps & games.
I think I’ve figured it out but I don’t know how all the materials went black & the lights went blank. I had changed material without realising I had done so, went back to the previous material although at first nothing changed but after looking through settings to make sure what I might have changed it appeared to be there again.
Question though, how do I remove the lightcap ? Also can’t find how to reset all materials either.
You have a knack for seeking out the more complicated aspects of Zbrush 
First of all, it’s important to understand the difference between standard Materials and Matcaps. Matcaps (the materials you see in the upper part of the material list) are materials (shaders) with the lighting information baked in. They are designed for quality surface feedback while sculpting, and quick preview without having to set up complicated lighting. Their lighting info will not update with changes to the scene lighting. When you assign a lightcap, you are altering the lighting information for a single material, not for the scene. If you want materials to interact with scene lighting, use the standard materials in the lower part of the list, and the original Lighting controls.
There are sometimes glitches with the Lightcap system, but I have no idea if that is what is happening here, or is just run of the mill user inexperience.
As far as restoring material settings, material changes should only save if you save your work as a .zpr project file (File> Save As). If you only save the tool (Tool> Save As ), then only your tool geometry is saved, and it will load into zbrush with the program defaults the next time you restart or initialize Zbrush.
If you have been saving material changes in a project file and want to reset them without resetting other aspects of the file, you can select the material you want to overwrite, then load the original material on top of it. (Material> Load). For windows, you should find all the mats in Zbrush4r7/ZData/Materials.
First off, thanks for the reply. Second, I’ve already learnt all of what you’ve mentioned. Third, the LightCap is the same as the MatCap where it bakes the light info to the material, I didn’t realise it could be per material and thought something strange was happening. It is partially inexperience / partly ZBrush and partly my iMac due to an ever failing gfx card.
I’m only looking for a way to clear all the LightCap data.