Today we look at another type of common finish – Shellac

The Product

Shellac comes from the secretion of the lac bug in SE Asia.   These secretions coat branches of trees.   The branches are exposed to heat (e.g., a fire) and melts and drips off.   This is called seed-lac, the least refined form and may contain contaminates such as dirt, bug parts, bark, etc.   Following this, it may be refined and bleached, yielding more and more types of shellac – garnet, orange (AKA amber), lemon, blonde (AKA clear), super blonde.    You can buy the product as “buttons” or as flakes, or you can buy it pre-mixed in its solvent.

Native shellac has some amount of wax in it.  If you are using shellac as a finish alone, it’s not a problem, but if you are going to top coat with another finish, you may want a dewaxed shellac to improve adhesion of the top coat.  You can see the wax settle out to the bottom of a container of shellac as cloudy.   Waxed shellac has less water--resistance than dewaxed.

The solvent for shellac is alcohol.   Normally we use denatured alcohol – ethanol (grain alcohol) with a bit of methanol (wood alcohol) added to render it unfit for human consumption

Shellac, like lacquer, cures by evaporation of the thinner and will re-dissolve in it.  As a benefit, when you apply multiple applications of a shellac, it melts into the lower layers and becomes in essence, one layer.  Compare this with a varnish where the layers remain separate.

Shellac was a common finish used in production furniture and cabinetry for 100 years until the introduction of lacquer following WWI.   By WWII, lacquer had mostly replaced shellac as production finish.   The introduction of synthetic varnishes following WWII for the hobbyist further reduced the demand.

Zinsser if the major importer of shellac products from Asia via Germany where most of the refinement is done.  There are a few “boutique” suppliers of shellac products.

Characteristics

Shellac is a fast drying and hard finish.  It is slightly acidic.

Shellac is usually listed by “cut.”  For example, a 2 pound cut is two pounds of flakes in 1 gallon of alcohol.  You don’t need to mix a whole gallon though, just as much as you need.   For example, if you need a bit  of 2 lb cut, mix ½ lb in one quart, or ¼ lb in one pint, etc.    Add the flakes to the alcohol, mix or shake periodically and allow to sit for a few hours to overnight.   Prior to use, filter with a finish filter to remove any impurities and undissolved resin.   Do not use metal cans for this as the shellac can react with the metal.   I like to use jars that pickles or tomato sauce has some in because the lids have an acid-resistant liner.

You can dewax your waxed shellac by letting the wax settle out, then decanting off the top.  However, I prefer not to throw away half the product when I can just buy dewaxed flakes.  SealCoat and Zinsser Aerosol Shellac come dewaxed; Bulls Eye (also from Zinsser) Amber and Clear are waxed shellacs.  Bulls Eye are 3 lb cuts and shelf life about a year.   SealCoat is a 2 lb cut and longer shelf life.  Canned and flake shellac:

(photo credit Popular Woodworking / Bob Flexner)

The price of shellac has increased in the last few years because of “crop failure.”   It is slowly inching back down after some better years.

One drawback of shellac is shelf life.  Once dissolved, it slowly degrades by a process called esterification.  The result is the finish will never fully harden.   Test home-mixed shellacs after six months and watch carefully after 12 months.  Test by putting a puddle on some wood and check in few hours.  If it’s not hardened by then, it probably won’t ever fully harden, throw it out.  So if you are mixing your own, don’t do more than you will need in the short-term and label the mix date.   Pre-mixed shellac, Zinsser Seal Coat (used to, no longer does) guarantee 3 year shelf life from point of manufacture, and I’ve used some 4 years old with good results.  Unfortunately, they, from time to time will change their dating code and what you pick up at Home Depot may already be past its “use by” date.  http://www.popularwoodworking.com/woodworking-blogs/flexner-on-finishing-blog/user-unfriendly-zinsser-bulls-eye-shellac.

If I’m refinishing a piece and even suspect silicone oil contamination from Pledge furniture polish, I’ll apply a coat of shellac before moving on to my selected finish.   Also if I’m working on a resinous wood like teak or aromatic cedar (that can affect and soften finishes), I’ll add shellac as a barrier.  If the wood smells, either on its own or by external factors such as urine, Shellac will seal it in.  Shellac will seal in the resins of pine knots that will otherwise bleed through the finish (especially obvious with paint).

I do a lot of water-borne finishes.  These can be sort of cool, almost blue, unlike the amber that we’re used to.  They may also not bring out some of the grain depth and shimmer (chatoyance) that we love to see.  A coat of two of shellac under the w/b finish will add good looks to your finish, especially if you are not using a stain.

Pros

• Very fast drying, 30 minutes or less
• Very fast application when spraying
• Color from clear to darker, depending on degree of refinement
• Hardness facilitates rubbing out to a high gloss sheen (or any other sheen)
• Easy to repair
• Easy to strip
• Compatible with almost any top coat (when shellac is de-waxed)
• Excellent “barrier coat” sealer for knot resins, odors, wood extractives, silicone contamination, wax,
• Seals in smoke, pet urine, or musty odors inside vintage case goods.
• Adds beautiful chatoyance to woods, adding depth and “dancing figure.”
• Can be used (highly thinned) as a wash coat to control stains
• Can be used as a sanding sealer coat
• No lingering smell so perfect for insides of boxes and cabinets
• Does not darken or orange with age
• Available in different colors from garnet to super-blonde

 

Cons

• Generally only available in gloss, though you can rub out to a lower sheen.
• Not as much resistance to water, alkalis, or alcohol
• Applied too thickly, it can become brittle.
• Limited shelf life once dissolved.

 

Application
Like most finishes, there are three ways to apply shellac.   I find the first coat of shellac will raise the grain a little bit.  So I sand after it’s dried and has stiffened the fibers up (“burying the grain.”)

Spray
Spray on coats overlapping half as you go.   It is not necessary for each coat to fully dry before adding another coat.   Air movement will help the evaporation of the solvents.   Shellac is available in aerosol cans for small jobs.

Brush
You can brush on shellac easily with a natural bristle brush.   Just don’t put it on too heavy on each coat or it can curtain or run.  Get it on and don’t keep going back over it because It dries so fast. You don’t even need to clean the brush,  just let it dry and put in a can of denatured alcohol.  If you do want to clean the brush, rinse in denatured alcohol.  You can also mix up some TSP in water and wash the brush.  The alkali in TSP will break down the shellac (and turn it purple.)  Most foam brushes will not work for shellac.

Cloth
You can pad on shellac. I’ve used this to restore an old finish after cleaning, abrading, or removing blush.   Lightly dampened rag wiped quickly.  There’s also an advanced method called “French Polishing” that combines shellac, a bit of abrasive such as pumice, and a bit of oil for lubrication.  Continuous wiping with a rag where the finish dries in what is described as “comet tails.”   Essentially thousands of applications of the finish built up to a high-gloss, high-end finish.  Not one I’ve even tried, no less mastered.

Fixing Goofs

Drips and runs are easy to repair.  Let them harden, sand or scrape level and apply another application which will dissolve and blend into one coat.

Another common problem is blushing.  This occurs in hot & humid conditions where the water vapor gets trapped in the finish while the solvents evaporate.  Finishes that have been on for many years tend to blush (water mark) easier.   Wipe with a rag dampened in alcohol and the blush will normally disappear before your eyes.   If you wish, pad on a top coat to restore the luster.

 

Summary: Try it, you’ll like it.

 

Further reading:
http://www.popularwoodworking.com/article/the_case_for_shellac
http://www.woodshopnews.com/columns-blogs/finishing/502292-shellac-as-a-sealer-its-all-just-hype
https://paulsellers.com/2011/04/how-to-apply-shellac-as-practical-wood-finish/
http://www.naturalhandyman.com/iip/infpai/shellac2.html

 

I am learning so much from these posts- Thank You!!

14 minutes ago, lew said:

I am learning so much from these posts- Thank You!!

Same here!

Ditto! Thanks for taking the time to do these mini-moments. They are invaluable, Keith.

Just an observation: I spray most of my shellac because it sprays so well. To clean the gun I don't use DNA, tho. The DNA will do it (sort of) but you still have very minute traces of shellac left in the gun (at least I do). Use household ammonia instead. It's cheaper, it absolutely destroys the shellac (none left in the gun at all), and all it take is a cupful more-or-less in a 5 gallon bucket of warmish water. the only watchout is that ammonia will stain aluminum, so you cup may get some discoloration, but it doesn't impact it in any other way. After the ammonia wash i usually do a soak in clean water to make sure I've removed all the ammonia, wipe it dry (again, sort of) and set it aside until the next time. the ammonia also works on brushes and so on, but as Keith mentioned there's little need to clean the brush if it's dedicated to shellac use. One other tidbit, I store my mixed shellac in a jar (canning jars with plastic storage lids) and I think there is a reason to do this, but I don't remember why. I do know it keeps fairly well in the jars.

Edited July 28, 20178 yr by Fred W. Hargis Jr

More tidbits. I saw recently in I think Flexners column in Popular Woodworking that the new Eco alcohol is better than the old denatured for shellac solvent. I picked up from Mickley on the old Wood forum that garnet shellac is good to even color out on cherry even when sapwood is present.

I used to store in canning jars and due to the constant problem of getting lids off I switched to medicine bottles. Plastic such as 3 to 4 oz antihistamine bottles (advantage being a pharmacist) and the plastic tops do not stick. Ask at your pharmacy for through aways or as for RX oval. 

I have done a french polish on a few items, such as a side table and deco bookstand. It is a learning curve and sometime need to back off and start over.