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Issues with Shellac finish of the hull

M

mrsamimi

Joined
Oct 28, 2024
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Hello Everyone, I am building Occre Santisima Trinidad, I used Shellac, Zinsser Bulleye Sealcoat and applied 4-5 coats as sealer and finish for the mahogany hull, I love the outcome, Let each coat dry for 4-6 hours and final coat for 3 days.

The issue I am facing is, after setting the model upright on Occre workbench, Although the cloth is soft, after a day it left some marks in finished Hull, can be seen like a missed spot or worn off, where the pressure is applied, what should I do? Is this normal? Should I apply another coat or two and let it dry longer? Or should I use Poly or maritime Varnish on Shellac, my product is wax free so I think you can apply any Varnish finish on it, anybody else experienced something like this?

Any help or comment would be appreciated!
 
My experience with Shellac is limited... but after 4-5 coats, you should have coverage. My GUESS is that you are seing variation on gloss. Shellac after multiple coats can be a little glossy (semi). I would leave it another couple day to full dry and cure and then apply a single (last) coat of poly (matte, semi or gloss) to your preference. Poly will stick to cure Shellac and should even out everything.

Wait for a couple other replies... someone(s) may have come across an identical issue that you and have a better solution.
 
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I mix my own Shellac from flakes.
A wet finger calculation has it that 10 lb cut is 10%.
This makes mixing the flakes easy. A digital pocket scale and a 100ml graduated cylinder......

I have never used Sealcoat version. I thought it was a one coat primer. It is probably too concentrated for even that. The first coat of Shellac should be 50% of saturated - 1:1 dilution with alcohol. I use 100% isopropyl alcohol because it is heavier than ethyl alcohol - 3 carbon atoms instead of 2 carbon atoms. Theoretically it should evaporate more slowly - being heavier. I doubt that the difference is significant in practice.
For Sealcoat it is the light color that is its marketing deal. It is probably super blonde - it is 20 lb cut - it is not the ultimate de-waxed. Platina is.
Zinsser clear is 3lb cut so probably Blonde. Zinsser amber is also 3lb cut so it is not a saturated solution. Looking at the MSDS it is 25% isopropyl and 5% MIK (I hope it is safer than MEK)

It is the wax in Shellac that is the dark factor. The more wax removed - the lighter - and the more expensive. The wax is also a solubilizer.
The lighter is the Shellac the less soluble in alcohol. The super blonde that I use is saturated at 20%.
I found these grades of flakes
Garnet
Amber
Beige
Blonde
Super blonde
Platina -

The more layer of Shellac, the deeper is the glass-like layer on top. The more glossy it becomes. For a ship model, you should want something a lot less than high gloss. Unless you want it to be toy-like. You should also not want to put a layer of plastic on it = polyurethane. Even more toy-like.
No one is going to walk on your model. No one is going to set a sweating glass of liquid on it. Nothing should touch the surface. It should be in a case -unless you intend to toss it out after 10 years or so.

What I would do:
I sounds like your Shellac layers were way too thick. Shellac should not dent or pickup a cloth weave pattern. What you did has to go!
Wet a piece of worn out 100% cotton tee shirt with 95% ethanol (Shellac thinner) wipe it down. Toss the rag in an empty qt. paint can you have the lid for. Get a new cotton rag and wipe again. Keep doing it until the bare wood is there.
I am pretty sure that it will still be primed. You would probably have to submerge the model in a bucket of ethanol to get that out.
Get a small can of pre-mixed clear Shellac. (Unless you want to go hard core and use flakes.) Wiper the surface with the Shellac using the soft 100% cotton rag - a pad of it. Just wet - no more - no streaks - no puddles - just barely wet. It dries fast. As soon as it is dry another coat can go on. Three or four coats should be more than enough.
Something I intend to do. Apply a layer of Renaissance Wax on top.
If this interests you: on a board that is sanded the same as your model:
give it a coat of 1:1 diluted clear Shellac
Give it as many layers of straight Shellac as you have given the model.
Give a coat of Renaissance Wax. If you like the look - there you go.
 
Indeed, I would try Jaager suggestion of wiping out most of the top layer with clean white rag soaked in alcohol (Denatured alcohol is the solvent I used with shellac flakes) ... but would not soak the ship. It does not matter what already polymerized in the wood, you are trying to "smooth" out the upper layer, so it is uniform (mostly removing the surface layer already applied).

In application, the smaller the better... a slightly moist rag in shellac, roll in a ball + wrap with a single layer cloth, and apply lightly going back and forth. You should barely see a layer on application.... just the wood seen very lightly moist.
 
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Loracs said:
. It does not matter what already polymerized in the wood,
Click to expand...
I was being absurd. I would never suggest soaking a model in anything. If he used PVA -it would be a bucket of loose parts.
I was explaining why the initial 1/2 concentration Shellac priming step was not needed for his redo.

Shellac just dries as a film, a layer - no reaction. Lacquer dries. Hide glue dries. Polyurethane polymerizes. PVA polymerizes. CA polymerizes - or something like that - some sort of water catalyzed reaction. Plant based oils (Linseed, Tung, Walnut, etc.) polymerize - unless the layer is too thick - then it is just a mess. For Linseed oil to dry in the lifetime of a human a heavy metal catalyst is added (Cobalt usually). For Linseed this is called "boiled". Tung also comes "cooked" 3 levels of polymerization - the longer cooked the more gloss. It may play nicer if it was spiked with Cobalt drier.

Loracs said:
In application, the smaller the better... a slightly moist rag in shellac, roll in a ball + wrap with a single layer cloth, and apply lightly going back and forth. You should barely see a layer on application.... just the wood seen very lightly moist.
Click to expand...
Your description is more specific, emphatic, and detailed than mine. It is more effective in getting the point across.

I have an old furniture finishing book that calls it French polish if there is a cotton ball wet with Linseed oil in the middle of the Shellac pad.
Then it is do not stop or overlap.
 
Can I sand down the hull? Or have to be cleaned with alcohol?

Also, Can I apply a final layer of Matt Poly to finish this without cleaning or sanding? Trying to find the best way fixing this.
 
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mrsamimi said:
Can I sand down the hull? Or have to be cleaned with alcohol?

Also, Can I apply a final layer of Matt Poly to finish this without cleaning or sanding? Trying to find the best way fixing this.
Click to expand...
There is no need to sand. You have a gummy layer that will clog sandpaper anyway. An alcohol cleaning is easy and should not take all that long. Be meticulous - get down to wood.

Sorry to read that you consider matte poly as an option. Conceding that, covering what you have with a layer of rigid plastic will be similar to putting a pane of glass over a block of Jello.

Google AI says:
" For a matte shellac finish, use a
Light Grey (7448) Scotch-Brite pad (Ultra Fine, ~800 grit) or even finer like the White (7445) pad (Micro Fine, ~1200-1500 grit) with paste wax for a smooth, satiny, non-glossy look, often after initial leveling with finer sandpaper (like 320-400 grit) between shellac coats. The goal is to dull the gloss without adding shine, working with the grain." NAPA or a competitor for the pads I think.
 
Thank you, I will try cleaning either alcohol, is it safe to say even top layer removed this may be better and cured over time? I am worries alcohol will damage the hull
 
DAWarden-(Jaager) said:
There is no need to sand. You have a gummy layer that will clog sandpaper anyway. An alcohol cleaning is easy and should not take all that long. Be meticulous - get down to wood.

Sorry to read that you consider matte poly as an option. Conceding that, covering what you have with a layer of rigid plastic will be similar to putting a pane of glass over a block of Jello.

Google AI says:
" For a matte shellac finish, use a
Light Grey (7448) Scotch-Brite pad (Ultra Fine, ~800 grit) or even finer like the White (7445) pad (Micro Fine, ~1200-1500 grit) with paste wax for a smooth, satiny, non-glossy look, often after initial leveling with finer sandpaper (like 320-400 grit) between shellac coats. The goal is to dull the gloss without adding shine, working with the grain." NAPA or a competitor for the pads I think.
Click to expand...
Thank you so much, great info, what I am
Terrified is, the hull has wood putty that filled cracked, been weeks since ai applied the wood putty so ai expect it to be fully dried, will alchohol destroy the wood putty? That will be disastrous for me
 
Do not flood with alcohol. Do not use enough to drip. Just a wet rag. remove the Shellac in layers. Go slow.

The standard debonding agent for PVA is isopropyl alcohol. But methanol, ethanol, and isopropanol are are all alcohols. They all share mostly the same chemical characteristics. Ethanol will debond PVA. I am believing that there is a layer of wood veneer planking between the wood putty and the Shellac? With two layer POB hulls, any putty is for dips and hollows ON the surface of layer one. If the hollows are deep, wood scabs PVA bonded and filed-planed-sanded should be used instead of a thick layer of putty. Unless the gaps between layer one planks are Grand Canyon scale wide there is no point in filling narrow gaps with putty. It has no effect on layer two and should be hidden by layer two anyway.
If the gaps are wide enough to affect layer two - it means that layer one was done very very wrong. It needs to be debonded and done over and done properly. If layer two needs putty between courses of planking. It was not done properly. It needs removal - new and wider planking stock obtained and the planking done properly.
 
DAWarden-(Jaager) said:
Do not flood with alcohol. Do not use enough to drip. Just a wet rag. remove the Shellac in layers. Go slow.

The standard debonding agent for PVA is isopropyl alcohol. But methanol, ethanol, and isopropanol are are all alcohols. They all share mostly the same chemical characteristics. Ethanol will debond PVA. I am believing that there is a layer of wood veneer planking between the wood putty and the Shellac? With two layer POB hulls, any putty is for dips and hollows ON the surface of layer one. If the hollows are deep, wood scabs PVA bonded and filed-planed-sanded should be used instead of a thick layer of putty. Unless the gaps between layer one planks are Grand Canyon scale wide there is no point in filling narrow gaps with putty. It has no effect on layer two and should be hidden by layer two anyway.
If the gaps are wide enough to affect layer two - it means that layer one was done very very wrong. It needs to be debonded and done over and done properly. If layer two needs putty between courses of planking. It was not done properly. It needs removal - new and wider planking stock obtained and the planking done properly.
Click to expand...

Thank you so much for taking the time
And providing great help and info, much appreciated, one last question, If i leave the model upside down for a couple of weeks, do you think it will eventually dry completely? It can not stay uncured forever, right?,
 
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