How long to wait before applying Varnish? (acrylics)

[Kugane]

Does anyone know how long to wait before varnishing? I get extremely varied results on google ranging from 1 second after it is dry to 104 weeks.

I generally have been varnishing  my stuff a few hours to a day after I paint it, but I've read online that dry =/= cured, and by varnishing too soon, chemicals get trapped under the varnish which will cause discoloration over time. Has anyone ever had such issues or is it complete nonsense? (I personally haven't seen any discoloration, but then again, my stuff has only been varnished for approximately 1 year.)

[RuneBrush]

It depends entirely on the varnish and paints you're using.  Generally GW paints dry and cure time is relatively short, I've hit them with a layer of varnish 15 minutes after putting my brush down with no ill effects.  Some paints (specifically airbrush paints) I tend to give half a day or more to a day to cure off, and certainly with Vallejo primers which I normally leave overnight before I put paint on.  If you've added medium of some kind that can also extend the curing time.  Forge World clear paints require 24 hours before doing anything to.

As for discolouration, I've only ever seen that when using a poor quality varnish and something that's been left in the sunlight for long periods (the UV messes with the varnish).  Apparently enamel's can go a little odd as they require air to cure.

[Kugane]

2 hours ago, RuneBrush said:

It depends entirely on the varnish and paints you're using.  Generally GW paints dry and cure time is relatively short, I've hit them with a layer of varnish 15 minutes after putting my brush down with no ill effects.  Some paints (specifically airbrush paints) I tend to give half a day or more to a day to cure off, and certainly with Vallejo primers which I normally leave overnight before I put paint on.  If you've added medium of some kind that can also extend the curing time.  Forge World clear paints require 24 hours before doing anything to.

As for discolouration, I've only ever seen that when using a poor quality varnish and something that's been left in the sunlight for long periods (the UV messes with the varnish).  Apparently enamel's can go a little odd as they require air to cure.

I did some testing. It seems when you varnish stuff that has only just dried less then an hour ago it can give some white discolouring here and there once the varnish dries, but generally after I let stuff dry for 6 hours that no longer occurs. It also seems that what people say that moisture will be trapped inside isn't entirely true, because the whiteness does get less over time.

I guess a lot of the varnishing 'logic' out there comes from people varnishing paintings, which sometimes need a year to dry before the first varnish is applied. So I guess thickness of the paint is the clue here. I checked painted stuff from people that complained about frosting when varnishing too soon as well, it seems many of them got very thick unthinned layers of paint on their minis. 

So I guess its possible to write a bit of a varnishing guideline sometime soon, but I need more points of data, lol. So far it seems: Thin coats > wait 6 hours. Medium coats > wait 24 hours. Dipping straight in the paint jar > wait 3 days lol

[RuneBrush]

You can also get frosting if you're using varnish from a spray can based on the atmospherics.  GW's recently released a new matt varnish (Munotorium Armour or something along that lines) that doesn't frost, so I'd be interested to see if that would make any difference to your tests.  Out of curiosity what varnish are you using?