Velveteen for replica plating

redfield at my-dejanews.com redfield at my-dejanews.com
Tue Sep 15 20:19:20 EST 1998


Hi Rafael,

Getting good velvet for replica plating is tricky.  I don't know of a
commercial supplier of ready-cut velvet for replica plating, but here's what
I've learned while trying to get good velvets for my lab.

First, you don't need molecular biology-grade velvet from a commercial
supplier. It's easy to cut velvet up into squares.  Just cut the squares a
bit bigger than the dimensions you want, because the edges will fray over
time, as they're repeatedly used and washed.  You can use pinking shears (ask
your mother if you don't know what these are) to minimize fraying.

The best fabric to use is upholstery velvet.  Velvet for clothing usually has
pile that's too long, and is likely to be nylon or silk, not cotton. 
Velveteen for clothing has short pile, but usually the pile is thin and
coarse. Upholstery velvet usually has lovely short dense cotton pile.

The problem with upholstery velvet is that modern supplies have usually been
pretreated with a stain repellant coating.  This makes the velvet also repel
water, and so it repels the liquid that inevitably oozes from the agar
surface when the velvet is pressed to it.  If this liquid isn't absorbed by
the velvet, it forms a liquid film that smears the colonies (you can see this
happening as you lift the velvet from the plate).  You can pretest any velvet
you are considering by squirting a drop of water onto it.  If the drop just
sits there, don't buy the velvet.  The stain repellant coating can't be
removed by laundering or dry cleaning.	Only buy velvet that immediately
absorbs the drop of water.

Best sources of velvet: -upholstery shops with old stocks of velvet.
			-old velvet curtains (one pair could provide enough
			 velvet for all the microbial genetics labs in Europe).

Good luck,

				Rosie

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