Rather than ask here, I’d write the manufacturer of the product and ask if they can give you directions.

Removing final layers on paintings can be tricky or easy. Gamblin’s GAMVAR picture varnish, for example, can be rather easily removed with OMS. If it were only that easy for everything else. I’m told removing dried/cured Liquin is nearly impossible and often fatal for the painting.

It is a risky procedure, but you can cover your sins after you remove the varnish by making corrections.

Waste a few minutes and watch this video:

https://www.youtube.com/watch?v=v0mYV_pMc0Q

Gamvar gloss.

According to what I heard, you could try using Mineral Spirits to remove it, very similar to clean a glass with a cloth?

If that does not work, try with True Turpentine. But please be careful and work in a ventilated area.

Gamsol or some other brand of Odorless Mineral Spirits / OMS is the only thing you should use to remove Gamvar. I would not recommend using turpentine or other strong solvents. Turpentine can dissolve some paint mixtures that have natural resins in them and can cause lifting of regular oils as well. Gamsol OMS is what Gamblin recommends on the bottle of Gamvar for removing it. I would highly recommend it over any other OMS if used indoors in the studio. It is one of or the least toxic and has the lowest offensive odors of all the various OMS options out there I have used. Hardware store OMS like Klean Strip or Sunnyside is pretty nasty smelling stuff compared to Gamsol, but it is cheap $15 vs $45 / gallon and will work to remove the Gamvar. You should have some fresh air exchange with all varieties of OMS but allow extra fresh air ventilation with the hardware store stuff, particularly when rubbing it all over a painting. Follow the instructions from Gamblin and as long as your painting was dry when you applied it, no paint should be coming off on the cleaning cloth.

A good clarification from WFMartin. If you see very slight amounts of color coming off on your cleaning cloth, don’t panic. That is going to happen with most paintings. However, if the paint is being disturbed and is clearly lifting off your painting to the the point that you can see it changing density on the painting you should stop and rethink your process. Try working with a softer cloth, softer touch, letting it soak a bit and using less rubbing, and / or use a less aggressive solvent unless you are already using Gamsol which is the least aggressive solvent easily available to artists. If your painting is fully dry and the paint layers are not underbound, you shouldn’t see the painting itself changing at all when you remove the Gamvar.

Ideally you should rub the painting with a soft cloth soaked in Gamsol BEFORE you varnish it, to see if it will hold up to the solvent. If it won’t, you may want to let it dry longer until it does. Be aware that some paint layers, particularly those that are sunken in and flat, are going to give off more pigment than shiny layers even after it has dried for a year or more. No big deal as long as your painting isn’t changing before your eyes or you aren’t toning other areas with the loose pigment. Change the surface of your cloth frequently to avoid unintentionally tinting other areas. It doesn’t take much pigment to tint the cloth – work in good light and pay attention to the painting more than the cloth watching for any subtle changes.

If your painting is touch dry, but not dry enough to varnish and it must go out to a show or competition you can use a thin isolating layer of Galkyd Lite applied as shown in the video link from Gamblin to unify the sheen of your painting and give you a touch dry surface without the worries of applying Gamvar too early. This method will significantly reduce the chance of disturbing your paint layers when a removable varnish is applied and then removed some time later. Most of my pieces with this final unifying layer applied have zero color lifting down the road when removing Gamvar with Gamsol. Galkyd will yellow less over time than oils or most other non alkyd materials such as Damar Varnish. Remember that it is a permanent layer that cannot be removed without damaging the painting.

You can send it out with just the Galkyd sealing layer and no varnish needed as soon as it is dry to the touch. If desired, you or the customer can apply a removable conservation varnish like Gamvar later.

He talks about using Galkyd diluted 1:1 with Gamsol as a thin unifying layer on a FINISHED painting at time stamp 2:45. The process is basically the same as the first part of the video. It should be very dry to the touch the next day. I prefer using Galkyd Lite diluted 1:1 for an even thinner unifying layer.

https://www.youtube.com/watch?v=zFJEzZkuls4

I’ve used “hardware store” oms with good results. Just go easy and don’t “scrub.” Removed it, let it dry overnight, fixed it, and re-varnished.