Woodworking Talk banner

1 - 20 of 23 Posts

·
Registered
Joined
·
3,478 Posts
Discussion Starter #1
I've been experimenting with waterborne finishes. Although I've had varying results with spray quality, I've found that sealing with shellac (Zinnser SealCoat) before top coating with the waterborne finishes gives greater depth. I've now learned that the waterborne finish that sprays the best recommends not using shellac for sealer. I thought dewaxed shellac was the anything under it anything over it sealer. Are there adhesion problems with waterborne finishes and shellac?
 

·
Registered
Joined
·
26,869 Posts
I've been experimenting with waterborne finishes. Although I've had varying results with spray quality, I've found that sealing with shellac (Zinnser SealCoat) before top coating with the waterborne finishes gives greater depth. I've now learned that the waterborne finish that sprays the best recommends not using shellac for sealer. I thought dewaxed shellac was the anything under it anything over it sealer. Are there adhesion problems with waterborne finishes and shellac?
What waterborne finish are you working with? Do they say shellac or sealcoat specifically. Most any finish will work well under sealcoat but not standard shellac.
 

·
Registered
Joined
·
1,222 Posts
I've been experimenting with waterborne finishes. Although I've had varying results with spray quality, I've found that sealing with shellac (Zinnser SealCoat) before top coating with the waterborne finishes gives greater depth. I've now learned that the waterborne finish that sprays the best recommends not using shellac for sealer. I thought dewaxed shellac was the anything under it anything over it sealer. Are there adhesion problems with waterborne finishes and shellac?
If you are starting with Shellac, why bother with WB?

You can get the same clarity, color depth and grain emphasis with Lacquer, or pre, or post cat for more durability. The application is far easier and faster than Shellac or WB.
 

·
Registered
Joined
·
1,222 Posts
If WB polyurethane is your topcoat, just use that for your sealer.



.
Reading his initial post, he is not pleased with the grain color depth using WB, hence the question not using it as the sealer.

I agree with you, if he wants to use WB, then use it as a sealer as well.

But, if that is not meeting his requirements, then why use WB?
 

·
Registered
Joined
·
25 Posts
I never had a problem; just make sure the surface is perfectly polished and dust free; apply shellac and WAIT a lot... even when it looks dry it might not be ready; after that clean it again and apply the spray (maybe a few coats to make sure it is well covered):thumbsup:
 

·
Old School
Joined
·
24,017 Posts
But, if that is not meeting his requirements, then why use WB?
He stated he had varying results. IMO, shellac is a poor base for a topcoat, or as a topcoat. He may not have had a sufficient build. WB polyurethane should be sprayed in thin wet coats. Being impatient, or not willing to provide the regimen for a good topcoat, could be the reason.

I get very good clarity and the look of depth.






.
 

·
Rick Mosher
Joined
·
1,010 Posts
WB coatings do not burn into previous coats so if you do not scuff the shellac properly the WB coating won't adhere. Target Coatings makes a WB shellac specifically for their WB coatings. That said if it is the color of a solvent base finish you are trying to achieve a thin dye stain before sealer will give you exactly the same look without using shellac.
 

·
Registered
Joined
·
1,222 Posts
WB coatings do not burn into previous coats so if you do not scuff the shellac properly the WB coating won't adhere. Target Coatings makes a WB shellac specifically for their WB coatings. That said if it is the color of a solvent base finish you are trying to achieve a thin dye stain before sealer will give you exactly the same look without using shellac.
By now I have experimented and used all the Target Coatings products. I use the EM7000 high build Lacquer most. You do not have to sand in-between coats.

I use their Em1000 WB sealer.

Using gloss and buffing down to satin gives me almost the grain popping effect as good old nitro, but not quite.

The problem is with Cat Lacquer, I can seal, sand, three final coats in about 1 1/2 hours. With WB, including the extra buffing that takes half a day.
 

·
Registered
Joined
·
1,222 Posts
The OP is applying WB over solvent based shellac, yes you do need to scuff unless you want it to peel off in a sheet.
I misread your post. You are correct about sanding the seal coat.
 

·
Registered
Joined
·
3,478 Posts
Discussion Starter #15
I just heard back from General Finishes and it appears that the key is to sand the shellac as Rick astutely pointed out.

I want to achieve the look of nitrocellulose without the volatility and health risk, that's my attraction to WB. I've tried a few so far. One had incredible depth, but didn't spray well. The latest (GF Enduro-VAR) sprays nicely, but doesn't have quite the depth of nitro, which is important to me on highly figured woods. I think a coat of shellac will help with that. I've got a test underway, I guess I'll see how it turns out.

As a side note, I've read that although WB finishes don't technically "burn in", they do cross link to themselves if re-coated within a certain time window.
 

·
Registered
Joined
·
26,869 Posts
I wouldn't recommend multiple coats of shellac but I think a single coat is a good idea. The shellac would seal the wood so the water in the finish wouldn't raise the grain and if an oil stain was used the shellac would provide a barrier coat to prevent a reaction between the linseed oil and the wb finish.
 

·
Registered
Joined
·
155 Posts
If you are starting with Shellac, why bother with WB?

You can get the same clarity, color depth and grain emphasis with Lacquer, or pre, or post cat for more durability. The application is far easier and faster than Shellac or WB.
I guess I'm just too "old school" to use WB/ lacquer finishes. I see no advantage in it's use except easy soap and water clean up. What am I missing?:blink:
 

·
Registered
Joined
·
1,222 Posts
I guess I'm just too "old school" to use WB/ lacquer finishes. I see no advantage in it's use except easy soap and water clean up. What am I missing?:blink:
I occasionally use Shellac for food grade finishes on lathe turnings. It is a very fast finish for wipe on, on the lathe and buffing out. Can do the whole job in 15 minutes.

Then it sits in my shop until I end up throwing the can away.

Shellac is less durable than Lacquer, much less durable than WB or Cat Lacquer.

I spray almost everything I make and I find Lacquer by far the easiest to spray, the color depth is the same as Shellac. WB takes me the longest and most work to spray, but it has advantages in not yellowing over time. So for a figured white Curly Maple, preserving the natural white color I will use WB. I cannot get the same color depth with WB, close, but it just feels and looks more plastic. It depends on the type of piece one builds. For cabinet work, no one will really see the difference between the three finishes.
 

·
Rick Mosher
Joined
·
1,010 Posts
I guess I'm just too "old school" to use WB/ lacquer finishes. I see no advantage in it's use except easy soap and water clean up. What am I missing?:blink:
Most people on this forum are doing their finishing in their home or garage and don't have access to a professional spray booth with explosion proof electrical fixtures and sprinkler systems, therefore the main advantage would be to keep hazardous fumes out of the living space and not burning their house or garage down!

By the way, I hope those of you who are using BLO or Watco type oils (even those wiping oil based finishes with a rag) are disposing of those oil soaked rags properly or you could burn your house down as well due to spontaneous combustion.

https://www.youtube.com/watch?v=9yq6VW-c2Ts
 

·
Registered
Joined
·
1,160 Posts
>>>> recommends not using shellac for sealer.

The reason for that is that shellac contains a natural wax the reduces the adhesion of oil based and waterborne poly varnishes. If you used a dewaxed shellac you do not have any concerns with adhesion.
 
1 - 20 of 23 Posts
Top