Gilding over cast resin

[grahamg]

Hi all, and a Merry Christmas to you all!

It's been a while since I've been here, but I'm back making frames. I have one I've been slowly working on for quite some time now. It's a version of a Kit Kat club frame, which is mainly constructed from pine with applied cast resin decoration. It will be gilded, in either imitation gold or genuine silver, depending on cost.

I'd really like to water gild it, or parts of it at least, but I'm concerned about the adhesion of the gesso to both the pine (DIY store stuff) and the resin. I know you can apply shellac first to provide a key, but I was wondering if anyone had had luck trying this method?

Thanks in advance,

Graham

[prospero]

Best thing is to try a small section first. Never done this but if I had to I think I would wipe it all over with white spirit to remove any greasy traces and gild straight onto the resin using acrylic size.
It will either work or not.

With the pine sections you would either have to build up gesso or use multiple coats of ripple paint topped with a basecoat of artist's acrylic which you can polish. Again, use acrylic size. You could in theory water-gild the pine sections, but I have my doubts about the resin parts.

Maybe some more experienced gilders will chip in.......

[vintage frames]

Nice to talk to someone doing something interesting. If it's a Kent style frame you're making, have you considered laying sand on the central flat area of the moulding? And if you're worried about the quality of the pine, do as Prospero says and "wash" it with some white spirit and allow to dry off. It's a good idea then to size all the pine with a coat of hot rabbit skin glue (rsg).
To apply the sand, coat the flat area of pine, all over with two coats of rsg and smother the whole frame with well dried "play sand". Then tip the frame up over some news paper and shake off the excess sand. You'll need to leave this to dry overnight.
Now is the time to gesso the frame. If you want to water-gild the outside wall of the frame, then you must only use real gesso. Don't go anywhere near the wood with shellac; this creates a non-permeable barrier and will prevent your gesso from sticking. Two or three coats of gesso on the wood, a thin coat (25p'cent diluted) over the sand and no gesso over the resin. Gesso would only blunt the detail. Go ahead then and water-gild the outer wall of the frame.
If instead you just want to use imitation gold, then you could have used Prospero's famous ripple paint.
The frame is usually coloured with a red clay bole at this stage and then NOW, you can paint the whole frame with shellac. This provides a barrier to prevent the gold size from sinking in. You could use acyrlic size but I find it messy and sticky and prefer to use 3hour gold size.
I'll let you take it from here and wish you the best of luck.

[grahamg]

Thanks ever so much both! Dermot, I meant to say I was going to sand the flat part, which I've tried before with mixed success, but I've never tried your method. Also the tip for putting shellac on before oil gilding is very useful: I've not had much luck with oil gilding before, but that may be the reason why. I'll keep you all updated with progress, this has already been several months in the making... I'm sure I once read about shellacking pine before gessoing to stop the resin coming through, but I'm not convinced...

Thanks again, you've both been incredibly useful.

[vintage frames]

And thankyou for your comments. Where you may have read about shellac over pine, is what to do about the knots. Some people would seal the knots with "patent knotting" which is just strong shellac. I'm not sure if this would become a weak area under the gesso. What I do is paint on some PVA over the knot. This helps seal the knot and provide adhesion for whatever goes on top.

[prospero]

What people call Pine can be a moveable feast. The term covers a wide variety of species. Also it tends to vary a lot according to growth rate, etc. Fresh cut 'construction' grade pine is generally quite sappy. This can cause adhesion problems with paints and glues. If you left it in a stable environment for a few years it is much better to work with. But who has got the time? This is why I like to give the entire surface a coat of shellac, with and extra dab on any knots. On really big old knots I sometimes drill them out and fill the holes with a solvented wood filler. Dead knots should be filled anyway or they could drop out. The magic thing about shellac is that is organic and will allow the wood to breathe. Synthetic varnishes will only seal the moisture in.

Old gilded frames mostly do have a pine carcass. But the wood that was available then is a different to the stuff you buy nowadays. I have a lot of old boards in my shed which came out of the house next door. Some of it must be 200 years old. It doesn't look to good with 15 coats of flakey paint on it, but if you plane it up it is beautiful.

[vintage frames]

Interesting you say that about covering all the pine in shellac. If the shellac provided an impermeable barrier on the wood, then that would be unsafe to gesso over ( I am talking about real gesso here). However, I take your point about shellac allowing the wood to breathe. I've never tried it under gesso - always worried it would ruin a whole days work, but I'll give it a go on a sample piece of pine and see if the gesso stays when I burnish up the gold. As you say, pine was used regularly on frames in the past. I particularly like the weight and solidity it gives to a frame; obeche is a bit light and insubstantial.

Flakey paint frames are very on-trend, be careful what you plane down!

[prospero]

I wasn't advocating shellacing the wood if gesso is going to be applied. A coat of RSG will do the same job. But if painting shellac is very useful as it will stick to almost anything and being porous will still accept a water based paint.

[vintage frames]

Sorry, read you wrong. Yes, it's best to use just RSG as a primer on pine before applying gesso for watergilding. It's the knots that are the problem.

[Benhen]

Wonder how you got on??? I've just piled on RSG gesso onto some epoxy resin fake gold mouldings from the 70s in the hope of giving it the handmade loving craftsman look.
Nasty poxy stuff, the gesso popped up in days. Best place for the junk was the skip, not even the fire.

[vintage frames]

RSG gesso over resin - why would you do that?

[prospero]

Gesso is essentially water based. It won't stick to a non-porous surface. You need a barrier coat. You could try shellac, or failing that some rattle-can car primer. Either of these will accept a water based medium. As long as it sticks to the resin. Having said that, I wouldn't put gesso on top. You don't really need it unless you were doing water-gilding with real gold. You can gild it with fake gold leaf if you apply coats of acrylic paint and use a suitable size. You can get acrylic size which is intended for this type of leaf. The trick is to leave it to dry so it achieves just the right 'tack'. Usually you can a generous window when the size is just right. Should be instructions on the bottle.
Or you could use gold powder bound in varnish. Liberon gilt varnish will work. This method is more idiot proof. I do it this way.

[vintage frames]

I'm always going to promote the use of RSG gesso over any other medium base. It's an age old product and adaptable in so many ways. Using it opens the door to learning a whole new world of painting and gilding techniques.
How much can you learn by opening a tin of paint?

[prospero]

How much can you learn by opening a tin of paint?

Don't lever with a screwdriver while your other hand is in front.