From The Collaborative International Dictionary of English v.0.48:
Grainer \Grain"er\ (gr[=a]n"[~e]r), n.
1. An infusion of pigeon's dung used by tanners to neutralize
the effects of lime and give flexibility to skins; --
called also grains and bate.
[1913 Webster]
2. A knife for taking the hair off skins.
[1913 Webster]
3. One who paints in imitation of the grain of wood, marble,
etc.; also, the brush or tool used in graining.
[1913 Webster]
From The Collaborative International Dictionary of English v.0.48:
Grains \Grains\ (gr[=a]nz), n. pl.
1. See 5th Grain, n., 2
(b) .
[1913 Webster]
2. Pigeon's dung used in tanning. See Grainer. n., 1.
[1913 Webster]