The Last Blows Decide the Surface: Planishing, Flatters and Faces

Let the work drop to a dull red and then go over the surface with rapid light blows, overlapping each one, using a smooth slightly crowned hammer face. The low heat is the point. Hot steel moves under a blow, so planishing hot just changes the shape again; cooler steel takes a surface impression without flowing, which is what levels the marks. Keep the blows light and even. A heavy planishing blow leaves a deeper mark than the one it was meant to remove, and the surface ends up worse than before — which is the commonest way this step goes wrong.

A FLATTER is a block with a broad flat bottom face and a struck face on top. Set it on the work, hit it with a second hammer, and it delivers a perfectly flat impression exactly where you placed it. That removes the aiming problem entirely: you are not trying to land a moving hammer face flat, you are placing a flat surface and then hitting it. For a genuinely flat forged face it is far quicker than planishing and far better than grinding. A SET HAMMER does the same in corners and against shoulders, where a flatter's wide face will not reach. Both are struck tools, so they want a striker or a second hand — which is one reason smiths traditionally worked in pairs.

Look at your hammer face under a light. Nicks, sharp edges and rust all print into the work, and a sharp face edge digs a crescent into the surface on every slightly-off blow. Dress the face smooth and put a gentle crown and a radiused edge on it, then polish it. A crowned face is much more forgiving of a blow that is not perfectly flat, because the contact point moves rather than an edge digging in. Keep one hammer dressed and polished purely for planishing and never use it for anything else. Using the drawing-out hammer to planish undoes the point, because it is the hammer that has been taking the abuse.

Wire-brush the work while it is still warm, between heats. Scale brushed off warm comes away easily; scale hammered in is a pit that has to be ground out, as the batch-120 rung on what heat costs sets out. Then choose the finish deliberately. A brushed-and-oiled forged surface keeps the hammer texture and the dark scale, which is what most people want from forged work. Grinding and polishing removes all of that and makes it look machined. Whichever you choose, the piece needs protecting: bare steel rusts within days. Wax applied while the work is just too hot to touch soaks in and leaves a durable finish, and oil works too. The finishing batch covers the reasoning; this is the one case where the work is hot when you apply it.