Finishing question

[Ron Citerone]

I have always finished with one product at a time, most recently I have been using waterlox original first coat to last coat. I have read that people apply shellac first to many finishes. I am confused here because it seems to me that if you seal the wood with shellac or any finish other than the one you will use on top would prevent the top coat from soaking into the wood getting the best advantage of the top coat. ???? thoughts

[Jim Becker]

Most of the time when I use shellac, it's to act as a barrier coat between two dissimilar finishes. So if I apply dye and then BLO, I use a thin, sprayed coat of de-waxed shellac as a barrier coat to insure that the water borne finishes I spray on as top coats will have proper adhesion. If you are using oil based products like Waterlox, there's no good reason to seal the wood first unless there are some unusual circumstances.

[Ron Citerone]

Most of the time when I use shellac, it's to act as a barrier coat between two dissimilar finishes. So if I apply dye and then BLO, I use a thin, sprayed coat of de-waxed shellac as a barrier coat to insure that the water borne finishes I spray on as top coats will have proper adhesion. If you are using oil based products like Waterlox, there's no good reason to seal the wood first unless there are some unusual circumstances.

Agreed, did that recently for some"etsy style" signs for my daughters wedding....used shellac as a barrier between oil based stain and water based paint she was going to use for the art work.

I do read about finishing techniques that involve some type of initial coat different than the main finish. I just don't see the point for a good species of wood and a good finish.

[Doug Hepler]

Ron,

Agreed -- I don't think there is much point in "sealing" bare wood with shellac. The fact that "people do that" does not count for much if there is no reason. (Check out a typical sharpening thread if you need examples.) However, there may be a reason for a barrier coat, as Jim said, not only to keep stain or dye from running, but to improve adhesion if there is any invisible residue of an old finish.

Going beyond your original question a bit -- I have occasionally used a coat of lightly tinted shellac as a toning coat. I once preferred to use Trans-Tint in shellac rather than oil based dyes for that purpose although this preference is not as strong now as it once was. People who don't really enjoy finishing can get a bit of a build quickly and easily with multiple coats of dewaxed shellac. Shellac dries more quickly, and is easy to level and rub out. Then one or two coats of wipe-on poly can give a reasonably waterproof, durable and attractive finish without the need to learn good brush or spray technique.

Doug

[Wayne Lomman]

I agree with the use of a single product. If I use more that one product, it is part of a coating system with known compatible products from a single manufacturer. I am not at all a fan of coating procedures that use inherently incompatible products. I am aware that shellac can act as an isolating barrier coat. However, what this means is that you effectively have two distinct coating systems working independently. I am not comfortable with this despite my byline. Cheers

[Jim Becker]

People who don't really enjoy finishing can get a bit of a build quickly and easily with multiple coats of dewaxed shellac. Shellac dries more quickly, and is easy to level and rub out. Then one or two coats of wipe-on poly can give a reasonably waterproof, durable and attractive finish without the need to learn good brush or spray technique.

One must be very careful with this...shellac isn't supposed to be "built up" and a thick coating of shellac can cause all kinds of issues. Shellac is different that most other film finishes in that the best shellac finish is the thinest one that will do the job...and it's an art form to get that.

[Prashun Patel]

There are plenty of reasons to use shellac underneath another topcoat.

Sometimes it’s to impart color to an otherwise lifeless water based top coat. That doesn’t apply to waterlox.

On woods with varying areas of porosity the shellac sealing and then sanding allows the final top coat to go on more evenly. It allows you to put on a very thin, even layer of the top coat without building too rapidly in some areas.

Last, on large projects it can be a money and time saver. Two sprayed coats of shellac will dry very fast, allowing you to use perhaps only 3-4 waterlox coats instead of 6-8.

I use shellac as a base for cabinets and sometimes large tables.

[Patrick Chase]

I agree with the use of a single product. If I use more that one product, it is part of a coating system with known compatible products from a single manufacturer. I am not at all a fan of coating procedures that use inherently incompatible products.

In what way is shellac "inherently incompatible" with other finishes? Or are you saying that you don't like the idea of using shellac as a barrier layer between two other finishes that are incompatible with each other?

[Jim Becker]

Patrick, Wayne's advise is sound in a general sense, especially in the lacquer world where you always one to stick with one manufacturer for your sealer and your top coats. But I agree with you that with few exceptions, de-waxed shellac....when applied properly...is generally safe for most finishes that are commonly used these days.

[Wayne Lomman]

Coating compatibility is more than a case of will it stick or not. Different coatings expand and contract at different rates for example. In my work with the products I use, all factors are taken into account. It is unnecessary to use a coating system that needs a shellac layer to make it work. However, others are happy to polish using shellac as a part of their procedure. That's fine with me. What I am not fine with is everyone remaining uniformed about other workable ways to do things. I use a wide variety of coating products in both my work and my home shop. I have learned through bitter experience in the past that a coating system must be researched and understood before use. Here's an example from my life. About 4 years ago I received a specification for a job that had to be done in Tasmania and sent to tropical Darwin for installation. I took one look and said it won't work and don't touch the job with a barge pole as the client will crucify us. The client insisted and the boss signed the contract unconditionally. All the paint promptly fell off on site and it cost the company in excess of $100K. Naturally it was my fault for not telling the boss forcefully enough. Not something that is likely to happen in our hobby shops but is another reason why I use products that are engineered to work with each other and produce a unified coating system. Sorry Jim, there I go again! Cheers

[Jim Becker]

Not a problem, Wayne. The issue of wood movement over top of that makes it even more fun.

[Doug Hepler]

One must be very careful with this...shellac isn't supposed to be "built up" and a thick coating of shellac can cause all kinds of issues. Shellac is different that most other film finishes in that the best shellac finish is the thinest one that will do the job...and it's an art form to get that.

Jim

Shellac is great for multiple coats because, as you know, each coat fuses into the one before. Maybe shellac can alligator if applied before the previous coat has dried fully.

Have you tried multiple coats of shellac? I have. It gives results as I said. Here is a reference from an expert, Jeff Jewitt: "Three coats should be sufficient for close-grained woods like cherry or maple, but you may want 4-5 coats on open-pored woods like mahogany. Rub the finish out with wax and steel-wool as above." http://homesteadfinishingproducts.com/shellac-a-traditional-finish-still-yields-superb-results/

Doug

[Patrick Chase]

Shellac is great for multiple coats because, as you know, each coat fuses into the one before. Maybe shellac can alligator if applied before the previous coat has dried fully.

Have you tried multiple coats of shellac? I have. It gives results as I said. Here is a reference from an expert, Jeff Jewitt: "Three coats should be sufficient for close-grained woods like cherry or maple, but you may want 4-5 coats on open-pored woods like mahogany. Rub the finish out with wax and steel-wool as above." http://homesteadfinishingproducts.co...uperb-results/

It's difficult to speak meaningfully about the "number of coats" of shellac without first specifying the cut and the application method. I've certainly gotten myself into trouble by brushing on 4-5 coats of 1.5 lb shellac without aggressive leveling (1.5 lb is basically the heaviest cut I use for brushing). In contrast French polishing effectively uses many more coats than that, but with a very thin cut (due to the way the pad is pre-soaked before the shellac is added) applied by pad.

Jewitt's "4-5 coats" advice is at the end of a paragraph in which he describes brushing a 1-1.5 lb cut. As I mentioned above 4-5 coats at 1.5 lb starts to require leveling work, but I think it would work fine at 1 lb.

[Jim Becker]

Jim

Shellac is great for multiple coats because, as you know, each coat fuses into the one before. Maybe shellac can alligator if applied before the previous coat has dried fully.

Have you tried multiple coats of shellac? I have...

Multiple coats of shellac are just fine. But building it "thick" can be problematic. Some folks slather it on (in a heavy cut) like it's varnish and that can lead to, um...frustrations.

[Art Mann]

I think inexperienced woodworkers are being misled into thinking that shellac is almost a necessity to "seal" the wood. Sometimes, there is nothing to seal. I have used all sorts of clear finishes without using shellac as an undercoat and have never had a problem. The only use I have for it is a sanding sealer. I just choose not to use a finish schedule that includes multiple incompatible materials that must be separated with shellac. I will keep this technique in the back of my mind in case I need it but I have been doing finishing stuff in my crude ways for 40 years and I just don't have the problems shellac is supposed to prevent.