laminating horn

[stuckinthemud]

So I laminated two strips of horn with gelatin glue, after 10 hours I took the string wrap off and the joint fell apart, the glue was jelled but not set/dry even thought the glue outside the joint was totally dry.  Presumably a horn-to-horn joint needs a really long clamp time - any ideas how long to leave it to dry?

[BowEd]

Did you size it well with thin glue and let dry first?

[bownarra]

Was it still liquid when the last clamp was applied?
Gelatine itself works but the gel time is way short....
As Ed says you must size the horn and wood many times with 5% glue first. Until the surfaces are glossy. It can take upto 20 coats of sizing.
funnily enough I've just been sizing a set of horns to be glued up today.
You only need to clamp the joint for a day or so max.
The gelled glue is sufficient to hold the parts together but they will take a month to dry enough to carry on working.
Sounds like you did something very wrong!

[stuckinthemud]

Mmm, used 25 percent glue to size the horn , wondered why it only needed 4 coats of glue

[bownarra]

That will be why then!
Horn to horn is a difficult bond to get right.
Heat the parts thoroughly the first time they are sized to increase porosity and make sure the glue is at 65 Celsius.

[stuckinthemud]

When sized, final coat is 30 percent then clamp?

[bownarra]

Yes that is correct.
When the sizing is complete let the parts dry thoroughly for a day. When ready to do the actual glue--up heat the parts to around 40/50 deg. The heat will soften the horn and give you a lot more working time.
Good luck
I did my horn glue-up today of a Turkish bow. I made use of the sun in my greenhouse, ambient temp of 40 degs meant I had plenty of time to get it clamped up. Much easier than fighting the cold in my workshop.

[stuckinthemud]

Is there a danger of dust contamination if you leave them 24 hours before glue-up?

[bownarra]

The glue will be dry to touch after an hour or so. Once dry they can be brushed off.

[BowEd]

If your worried about dust I lightly covered my sized limbs with saran wrap before,but found it unnecesary if stored in a quiet area and left to dry a day or so.Glueing up within a week though.Oxidation can occur too.Still lightly sanding for freshness and brushing off dust before applying sinew or glueing core to horn.I wear cotton gloves through all this process while washing hands with dish soap before hand also.
Lightly sanding inbetween sizing and brushing off is a good idea too for smoothness reasons.It's important to pay attention to details.