Leather costrel question

[Baron Conal]

I've seen a couple websites from people that have recreated a costrel of this style.

Some have added an extra strip of leather into the seams
at the 'ends' of the costrel so that there are three layers in
the seams.

I can understand adding the extra leather at the spout
to make it easier to fit the 'cork/plug'.

THIS PAGE claims it helps to waterproof the seams.

I had no problems with watertight seams on the other
two bottles I've made and this seams like extra work.
( I've sealed with wax and brewers pitch )

Is it copied from surviving pieces and we do not know why
they added it? Or does it really do what he claims it does and
I got lucky on my work?

Or is it not really needed.....? or....?

[James B.]

The examples I know of have the extra piece in the sides, the handles for straps, and the spout. I am looking at the images of a costrel from Limerick City I have in front of me and it has all the mentioned layers.

I doubt they were all done that way. Things tend to vary more than people want to admit.

I am sure they help waterproof much like a rand in a shoe but also it makes the bottle stronger with all the leather on the seams and the pitch it will be a hard item to crush.

There is also a bottle shaped flask from Limerick City that is just 2 pieces of thinner leather than the costrel is made of.

[Kilkenny]

I tend to leave the welt out on the ends as well. I find putting it in along the top seam can help a bit with the joint at the end where the top seam and the end cap seam meet. Pulling the two layers of the top seam together and getting them tight to the end cap can be a challenge. An extra bit in there along the top eases that transition a bit.

I can't claim to have had a good enough look at a decent sampling of surviving exemplars to say whether they tended to do it one way or another more often.