I have been using ProtectaClear metal coating from
http://www.everbritecoatings.com/ to preserve the brushed finish and
patina on the base metals I work with (nickel, copper brass) which
was recommended to me by a contact from this list.
I previously used ZafonLack which has been yellowing and streaking
and cracking.
So far I have been really pleased with product and the service,
especially from Zoe, so I wanted to let readers of the list know
about it.
Laura
Laura Cowan
Judaica Designer
www.lauracowan.com
Laura
I too have been using the ProtectaClear metal coating from Everbrite
and have been very pleased with the results. Since it is used out of
doors on architectural metal on bldgs, etc. I figured that it would
work well on jewelry as well.
Debbie
Thank you Laura 
Does it affect the color of the patina at all?
marine varnish is a viable and far cheaper alternative,and is
available at most home stores. I however prefer a microcrystalline
wax,for a matte finish or carnauba wax and gum tragacanth
combination for a harder but still more matted finish as i don’t like
the gloss that those waterproof varnishes give everything- However,
if you want a glossy sealant,then marine varnish or protectaclear is
appropriate, if not the preferred coating.
Depends on the patina’s method of application and wether it is just
"floating" on the surface or “etched” into the metal too. If it is
strictly just on the surface a sealant is the only thing that will
preserve it: any rubbing will destroy or reduce the vibrancy of the
colourations if the patina has not bonded with the metal’s
crystalline structure, or resulted from the crystalline structure
being heat (or sometimes heat and pressure) or electrolytically
treated in which case the varying colourations come from “within” the
metal and are indelible. For those patina’s that are into the metal
it is a matter of taste and design as to whether a glossy or not
finish is applied.
rer
Go to a hardware or hobbie store and pick up a spray can of
Krylon Crystal Clear Acrylic Coating, come in gloss or matt
finish. Apply with light dusting coats, a little at a time. Follow
directions, works fantastic on patinas & hundreds of other apps. No
shop, artist, or what ever you call yourself, should be without this
product!!! Just mask off areas with tape or what ever necessary to
mask off areas you do not want spray.
Mike