grooving vs roughing up

[Mafort]

so im aware that grooving is the commonplace method to attach horn to a core but ive read that some horn strips were merely roughed up prior to gluing and my question is how was this done? where both surfaces roughed up with a heavy file and then glued together?

[superdav95]

Ive done lighter weight horn bows 50lbs and under that were only roughed up for the horn glue up.  anything over 60lbs i would suggest grooving for increased glue surface area.  I used 36 grit paper.  I have also used a gimping file too that worked well too.  a fine gimping file from my knife making days.  The most important aspect for good horn glue up using natural hide or sinew glue is good thorough sizing with very thin glue.  I also warm up my horn slats and glue surface while applying the first few layers of sizing glue.  this is the most crucial part of horn glue.  In my opinion it more important then grooving.  hope this helps

[Mad Max]

For a 1-1/4" wide bow.
with all the up down's with the groves, it would be about 2-5/8" of glue surface.
Twice the glue surface