I’m painting up some Raven Guard Primaris Intercessors squads where the sergeants have thunder hammers, and here’s the recipe I’m using to get the following look:
The hammer started off being undercoated in Mecha Black and a base coat of Hashut Copper was applied. A wash of Canoptek Armourshade was next and once that dried a heavy drybrush of Ironbreaker followed. The contact face of the hammer then received some White Scar and a drybrush of Praxeti White was applied, brushing from the face back so that it faded the further it went.
Calth Blue Clear was applied to the sides of the hammer. It dries a little more slowly than the Citadel washes so it’s a little easier to move it around to create a light to dark transition without having to get it right first time around.
Talassar Blue was applied closer to the face of the hammer to help with the transition, then Drakenhof Nightshade was carefully painted onto the face in the recesses and further back on the hammer where there were still lighter spots visible in recesses.
A little more drybrushing with Praxeti White and then some careful edge highlighting with White Scar got it to the point you see above.