Characteristics of Shellac
Pros
-Works great as a barrier coat between stains and finishes. It will adhere to almost any topcoat and virtually any top coat will adhere to it. If you are not certain what sort of finish was previously on the wood, or you suspect the use of silicone based furniture polish, shellac will seal off all this to insure a clean surface for your top coat to bond to.
-Dries fast – a first coat can be recoated in 30 minutes to 1 hour depending on temperature and humidity. Subsequent coats after that need about 8 hours to dry between coats.
-Dries with clarity: it shows off the grain of the wood.
-Is UV resistant. Will not yellow.
-Easy to apply with brush, pad, or sprayer.
-Covers stains and smells prior to repainting. Water, smoke, and tannin stains on interior woodwork can be prevented from bleeding through fresh paint – usually with just one coat of shellac. Pet and rodent odors can be sealed in on wood surfaces.
-The different grades of shellac can change the tone of your wood. Transtints can also be added to increase a color change.
-Unlike some other finishes,one coat of shellac “melts” into the previous one, so when you finish a piece with shellac you end up with a single layer of finish. The fact that an application of shellac 'melts' into the previous one allows for easy repairs.
-shellac is non-toxic for use on children's' furniture and for use around food. The fumes during application, being alcohol, are also non-toxic although good ventilation is recommended.
Cons
-shellac reacts to alkaline products such as ammonia and some household cleaners. These products should not be used on shellac finished furniture and should be used with caution around these pieces. For example, if a piece of furniture is near a window or mirror, care should be taken when using cleaners in spray bottles above the piece as spray can drift and mar the finish.
-alcohols such as perfume and strong alcoholic beverages will also affect a shellac finish. Of course it is always wise to use coasters for beverages on wood surfaces.
-shellac is sensitive to heat ( will soften at 150 degrees F ), thus hot objects should not be set on a shellac finished surface, nor should the piece be placed in strong sunshine or close to a fireplace or woodstove.
-water will leave a mark on shellac finishes if left for a period of time, although to a lesser degree on dewaxed shellac surfaces.
-tends to scratch more than some other finishes. A coat of furniture wax helps.
-all wood finishes have their disadvantages. The swell thing about shellac is all the above can be much easier repaired compared to a lot of other finishing products.
Shelf life
Once shellac flakes are dissolved in alcohol, it has a shelf life of about 6 months. I like to label the jar I store it in with the date it was dissolved. If there is a question regarding freshness put a dab on a hard nonporous surface. If the dab isn't dried hard in a couple of hours, discard that liquid and mix up a new batch.
-Some folks talk about using chemical- grade ethanol to mix with their shellac flakes. I myself have never run into any problem using the denatured alcohol from the paint or hardware store. You will know if there is a problem if you get “ blushing” when the coat has dried. Blushing will indicate that either your alcohol has water in it, or you are applying the shellac on a very humid day.
The Cut
With regards to shellac, the term “cut” refers to the proportion of shellac ( in pounds) to alcohol( in gallons ). Thus a 2 pound cut means 2 pounds of shellac flakes dissolved in a gallon of alcohol. Since few people would use a gallon of shellac for a project and because liquid shellac has a relatively short shelf life ( approximately 6 months ), it is best to mix up only what you think you will need. For example, to make a 2 pound cut you could mix ¼ pound of flakes with 1 pint of alcohol.
Below is a chart for mixing 8 - 10 ozs. of finish at various cuts:
#1 cut.....................1 oz flakes...............8 oz alcohol
#2 cut.....................2 oz flakes...............8 oz alcohol
#3 cut.....................3 oz flakes...............8 oz alcohol
Of course you can make a little over a pint of finish by doubling the flakes and the alcohol.
After the flakes have totally dissolved, the liquid will need to be strained either with a fine mesh paint strainer or tightly woven cloth.
When dissolving the buttonlac it is best to crush the buttons, as they will dissolve much quicker. I wrap the buttons in a clean cloth and smack them with a hammer. Perhaps you have a more creative method.
There are 3 ways to remove the wax from buttonlac:
Wrap the pulverized buttons in a double layer of large paper coffee filters. Tie the top closed and set this in the appropriate amount of alcohol.
Dissolve the pulverized buttons in the alcohol, then filter it through a couple of large coffee filters. This method takes time as the solution filters through slowly. There is also some alcohol evaporation.
Dissolve the pulverized buttons in the alcohol and allow the solution to sit for a number of weeks and then decant the dewaxed layer into another container. This method is the least recommended.
