Humbrol acrilic varnish - how do I remove this?

[chris251]

I made the mistake of airbrushing Humbrol acrylic varnish to some models today. The problem is that the varnish I used was number 135, satin finish, and it made the models all cloudy and greyed/whited out, and yet being modern prototypes, they need to be shiny.  The satin varnish is much duller than the satin Pheonix paint below it.

 

This might be caused by a matting agent, but enamel gloss cote varnish doesn't dissolve it completely, and I would like to replace the acrylic varnish for enamel gloss cote

Does anyone know how to strip acrylic varnish without damaging paintwork and transfers?

 

(Paintwork is all enamel apart from the black door seals which are acrylic), and the precision labels transfers which are coated above and below with acrylic varnish - I'm not so bothered about ignoring the varnish on transfers as a slight difference in finish on the transfers won't be so noticeable.

Also, would it create a weak-spot if the acrylic varnish can't be removed completely and so lies under enamel varnish in corners?

[Campaman]

Not sure how to remove it but below is some information regarding Enamels and Acrylics and over painting.

 

I think you will have problems if you just try enamel varnish over the acrylic

 

Can You overpaint acrylic paint?

If you try to overpaint an acrylic paint with an enamel paint, then the solvent in the enamel will lift the underlying acrylic paint. You can usually overpaint an enamel paint with an acrylic paint provided the enamel paint has fully cured and there is no solvent left in the enamel.

[Guy Rixon]

Try isopropanol. It's a common solvent for acrylic paints. My experience is that it softens acrylics even after they are supposedly cured. I don't know how much it would mess with the enamel paint.

 

PS: if the satin vanish has gone cloudy it's because the matting agent is caked up instead of finely distributed. No amount of over-painting with good varnish can change that, even if it makes the surface shiny.

Edited April 12, 2021 by Guy Rixon
Note on cloudiness of varnish.

[Torper]

Varnish can be problematical.  Due to problems in the past I now test any combination of varnish and paint before I apply it to a precious model (I have a few old vehicles which I tend to use as test pieces).  I was recently very happy indeed with the finish I obtained from airbrushed Humbrol Satincote, thinned as necessary with white spirit and used on enamel paint.

 

DT

Edited May 8, 2021 by Torper

[chris251]

Thanks for the advice

On 12/04/2021 at 13:34, Guy Rixon said:

Try isopropanol. It's a common solvent for acrylic paints. My experience is that it softens acrylics even after they are supposedly cured. I don't know how much it would mess with the enamel paint.

 I tried Isoproponol alcohol, and it does lift the acrylic varnish, but was worried it can also lift transfers, so avoided using it on the transfers leaving some acrylic varnish being over-coated with enamel.

 

On 12/04/2021 at 13:27, Campaman said:

Can You overpaint acrylic paint?

If you try to overpaint an acrylic paint with an enamel paint, then the solvent in the enamel will lift the underlying acrylic paint. You can usually overpaint an enamel paint with an acrylic paint provided the enamel paint has fully cured and there is no solvent left in the enamel.

I'd already painted over the acrylic varnish with enamel gloss cote (thinned with white spirit) before seeing these answers, and it's not lifted anything - hoping it won't gradually start to lift and ruin things at a later date! 

 

When you mention enamel solvent lifting acrylic, do you mean white spirit, or acetone/xylene as the solvent? - acetone/xylene seem to thin and lift almost any paint and I hate using it, so always use water or IPA for acrylic and white spirit for coach enamel.  Some enamel spray paints include acetone thinners, but Humbrol gloss cote from a jar uses white spirit.

[Campaman]

Its just a general rule of thumb, I have had enamel lift acrylic. I guess it all depends on the brand and type of acrylic and the type of solvent in the enamel as if it lifts it or not.

[Cunningham Loco & Machine Works]

Ordinary domestic ammonia serves well as a solvent for removing acrylic paint, but does not affect lacquer and almost certainly does not affect enamel. It is far superior to isopropyl alcohol insofar as it will not discolour your underlying solvent-base paint as isopropyl alcohol sometimes does.

[Torper]

On 13/04/2021 at 14:08, Torper said:

Varnish can be problematical.  Due to problems in the past I now test any combination of varnish and paint before I apply it to a precious model (I have a few old vehicles which I tend to use as test pieces).  I was recently very happy indeed with the finish I obtained from airbrushed Humbrol Satincote, thinned as necessary with white spirit and used on enamel paint.

 

But I'm not so happy now.  Certainly the SatinCote gave a seemingly perfect finish to the item I was painting (a 1/350 ship's hull) but some weeks later it was feeling just a trifle sticky - almost imperceptible, but not quite and a magnet to dirt.  So I've had to "wash" the hull with white sprit, which has removed the stickiness (and the dirt) but has left me having to paint the hull again.  I'm not sure why this happened - maybe I sprayed it on too thickly or perhaps I should have used Humbrol's own thinners rather than generic white spirit?

 

DT

Edited May 9, 2021 by Torper