Question on sealing hull before painting or applying copper plates, and paint finishes

[WalrusGuy]

I'm relatively new to wooden ship modelling and had a few questions on sealing the hull before proceeding to paint and copper plating my US Syren build: 

 

1) is shellac a good sealer before both copper plating and painting the hull?

2) how does shellac compare to primer? Is it ok to skip sealing the hull and paint on bare wood instead? 

3) after painting, is tung oil a good finish to go over the last coat of paint? Would I need to do this step if I seal the wood before painting? 

4) can i use tung oil to seal the wood before copper plating? 

5) why would one need to seal the hull prior to copper plating? 

 

Apologies if these questions seem too trivial. I haven't painted or copper plated wooden models before so wanted to get some clarification before attempting. 

[Paul Jarman]

I personaly use primer. I use straight forward sanding sealer if I need to.

I Would not prime or seal where the plates are glued on as bare wood will allow the copper to adhere better.

This also goes for any areas wherePE will be atached.

Paul

[Jaager]

This is my opinion.  I am not a professional in the paint industry or a professional cabinet maker. Do not take this as authoritative as it reads.    It is just easier to use an imperative verb tense in this case. 

 

1) Shellac is good to use as a primary coat before painting. Use 50:50 concentration as a first coat.  It fills small pores, penetrates the wood, locks down the surface fibers and leaves a very thin addition to the surface.  Steel wool 0000 ( be sure to remove all steel slivers or = rust/stain) or Scotch Brite leaves a smooth surface for paint and it saves a coat of paint. 

Copper plating ....  which type, how is it to adhere to the hull.  If it is adhesive backed foil, shellac may be a good surface.  If it is metal/ glue - bare wood AND abrasive clean any copper oxidation layer from the back of the metal.  If it is metal paint on bond paper, bare wood.

2) Primer can be dilute paint - shellac is a good base for any follow on - paint or clear.  If by primer, you mean sand n sealer - this is mostly for open pore wood species - like Oak, Walnut, and the stuff in a lot of kits.  It has particles of stuff like plaster to fill the pores and leave a smooth surface.  If you have used a good choice of the species for the planking, it is superfluous. No pores to fill.  Skip the shellac and you may need an additional coat of paint.  Since you are not painting the interior walls of a house, the additional cost of another coat of paint is nill.

3)  Tung oil is for a clear finish.  Shellac can go first, or 50::50 Tung oil : mineral spirits.  No point in using it over paint.  Too much gloss on the paint itself is often already a problem with models: scale effect.  Additional gloss from Tung oil would make this worse - unless it is a toy that you are displaying. 

4)  Tung oil is an oil.  It stays wet until it polymerizes.  It would be awful as a base for any type of copper plating.

5)  Beats the -ell out of me, why anyone would want to.  I sure would not go it.

[WalrusGuy]

Thanks so much Paul and Jaager. I'm using the kit's basswood which isn't an open pore wood species. Therefore I'll be skipping the shellac and instead will paint directly on it with thinned acrylic paint.

 

As for the copper plating, they have an adhesive back so I'm thinking of skipping applying sealer to the hull. 

 

Thanks again for the tips and advice! 

Edited May 10, 2020 by WalrusGuy

[Bob Cleek]

4 hours ago, WalrusGuy said:

I'm using the kit's basswood which isn't an open pore wood species. Therefore I'll be skipping the shellac and instead will paint directly on it with thinned acrylic paint.

 

As for the copper plating, they have an adhesive back so I'm thinking of skipping applying sealer to the hull. 

 

Jaeger is right. Unlike Jaeger, though, I'll use an imperative verb tense because I'm sure I'm right.

 

Seal your basswood with white shellac, two pound cut or so, right out of the can. (I use Zinsser's Bullseye brand. Shellac is cheap.) It only takes a few minutes to seal with shellac, which is very thin and soaks right into the surface of the basswood. (No worry about brush strokes. It's like painting with water and is invisible when dry, so long as you don't build up a lot of coats, which will then develop a gloss finish as multiple coats are applied.) Then, lighty fine sand your surface smooth as a baby's bottom, or use metal wool or a Scotchbrite pad. (But, perhaps obviously, don't sand so much that you remove all the shellac! If you "break through" the sealing, simply apply some more on top of it.) You will almost certainly not be able to get a perfect fine scale finish on basswood otherwise. The shellac hardens the fibers in the surface of your basswood and prevents "fuzz." If you don't seal your basswood, especially if you are using a water-based paint, the wet paint is going to raise your basswood "fuzz." In that case, at best, you will have to apply many coats of fine paint and sand the paint coating until it fairs the surface. This is tedious and often difficult to do well. 

 

As shellac soaks into the wood fibers quite well and doesn't peel or "let go," I see no reason why it should not be used as a sealer beneath adhesives used to attach copper plates, or anything else for that matter. Basswood gets a bad rap as "too soft" for modeling because sanding it "raises fuzz" and it is difficult to obtain fine edges on it. I have found that sealing basswood well with shellac essentially creates a "composite wood product" when the shellac soaks into the wood surface, making the surface much harder than when in its natural state. (The same can be done with CA adhesive, but at an exponentially greater materials cost, not to mention the health risks of large scale CA fume exposure.)

 

In no particular order of importance: Shellac is 1) an archival material that lasts centuries. 2) It's easily "undone" by cleaning off with alcohol. 3) Clean up is easy.  4) It's also an adhesive and very handy in "tacking" rigging knots and "stiffening" rigging line for various purposes. 5) It dries as fast as the alcohol evaporates. 6) It's compatible with all other finishes and adhesives, save, possibly, certain alcohol-based acrylics, which, like all untested proprietary coatings and adhesives, should be tested for compatibility before committing to application on a model.  7) Shellac is one of the best "organic" moisture barriers available. It inhibits rapid humidity cycling and so tends to greatly stabilize wood movement in the model to the great benefit of glue joints and rigging tension over time. For this reason, I generally shellac all wood on a model.  😎 If you are worried about such things, shellac is "organic" and safe for human consumption, not that I'd advise drinking shellac thinned with methanol. Shellac is actually used to put the "shine" on jelly beans and M&M candies so "they melt in your mouth and not in your hand." 

 

Shellac is really a material every ship modeler should have on hand and will likely make good use of.

[WalrusGuy]

Hi Bob, many thanks for the advice. I unfortunately have already started to apply coats of paint on the model. 

 

I'll definitely try to use shellac on my next model. In fact, my next model (Pickle by Caldercraft) will be sort of an experiment model where I am going to try different things. For example, I'll try making a pedestal stand, bending planks using an iron (ie. Chuck's method), and of course, applying shellac before painting the model. 

 

Thanks again for taking your time to assist me on this, it is much appreciated! 

[Beef Wellington]

I have attached copper plates directly to unfinished (other than sanded) wood without issue using higher viscosity CA.  One consideration is that using plates invariably leaves very slight gaps (probably depending on skill level!) so having a 'similar' colour underneath helps minimize the visibility of these imperfections.

[ErnieL]

Jason, that’s a stellar idea, one I will certainly use going forward. 

[Jaager]

It is possible to use a dye on the under the copper planking to match the color of the copper - especially the old penny end point.

Using alcohol based dye will avoid the fiber swelling factor with aqueous dyes.  Because it is hidden, the shallower depth with alcohol dyes is not a problem.  This has no effect on the wood surface v.s. bare wood.

 

I am not using slang, a dye is a totally different material from a stain.  A stain is semi transparent wood colored paint.  If your wood is quality, a dye offers options for display, without affecting the grain as viewed.  A stain is to improve low quality wood.  It muddies quality wood.  A thought that repeats is why expend all this time and effort using low quality wood, unless it is to be painted?

[wefalck]

Attaching real copper plates with CA can cause bonding issues, as the copper ions can interfer with the cross-linking process while the resin is curing. A contact cement is probably the more secure option.

 

In theory, the plates should overlap a tiny bit, so that the issue with gaps should not arise.