Could there be a better way to kick off a new blog than an article about bug crap? I don’t think so.
Shellac is a mostly forgotten wood finishing product that has been largely replaced with more modern varnishes, lacquers, and polyurethanes. It’s made from the secretions of a tiny bug that lives in South Asia, aptly named the Lac bug. Tree sap goes in one end and a sticky resin comes out the other. When this resin dries it becomes hard and water repellant. To apply it as a wood finish it is dissolved in pure alcohol. 100% ethanol is best, but unless you have your own moonshine business, you’ll have to settle for denatured ethanol. That is ethanol that has a small percentage of methanol (don’t drink it: you’ll go blind), isopropanol, or some other adulterant added to it so we don’t use it as cheap booze.
If you Google the word ‘Shellac’ it takes two pages just to get to the Wikipedia article about it because apparently ‘shellac’ nails are now a thing (note to woodworkers: these are the kinds of nails you try not to hit with a hammer). From an exhaustive 5 minute web search, I conclude there is actually no real shellac in fingernail treatments. They seem to be an acrylic gel of some kind that is light cured. According to this website: Chemistry Is Life which I totally trust because Maddy has really done her homework: “Shellac nail polish is a mixture of methacrylate monomers and radical initiators (benzoyl peroxide). When these two mix under the UV light they create a radical polymerization process.”
So why they call that stuff shellac is anybody’s guess. Anyway, what we’re talking about here is the real thing that is painstakingly gathered from trees and processed by farmers in India and Thailand. It’s all natural and edible, and was reportedly even used to make Skittles shiny before 2009 when they changed the coating, maybe to make them more vegan friendly? The pharmaceutical and confectionary industries use a lot of shellac to coat things so I guess we eat it all the time.
Here’s a nice old timey Story of Shellac if you are interested. And here’s an excerpt from the Zissner company that you can find over at the Natural Handyman site extolling the great properties of shellac. It is aptly entitled:
Shellac’s Great Properties
Shellac has such remarkable properties that if it were just recently discovered it would be hailed as a miracle finish of the 21st century.
- All-natural – Shellac is an all-natural resin of insect origin that is harvested regularly and is therefore a renewable resource.
- Fleeting alcohol odor – Shellac is dissolved in denatured ethyl alcohol. It has a fleeting, antiseptic odor that dissipates quickly as the product dries.
- Easy to use – Shellac is user-friendly and virtually goof-proof. It can be applied with a brush, pad, sprayer, or wiping cloth.
- Super-fast dry time – Shellac dries to the touch in MINUTES and, in most cases, can be sanded or recoated in a little over half an hour.
- Cold temperature application – Unlike other finishes shellac can be applied in cold temperatures (40o F. and below) without concern over proper drying and curing.
- Non-toxic/hypoallergenic – The U.S. Food & Drug Administration has certified shellac as a protective glaze for candy and pharmaceuticals.
- Non-yellowing/non-darkening – Shellac is UV resistant and will not yellow or darken with age – unlike oil-base finishes.
- Enhances the beauty of wood grain – Shellac brings out the rich warmth of wood grain. Finished surfaces look soft and natural, not plastic-coated.
- Sticks to glossy surfaces and finishes – Shellac is prized by everyone who uses it for its incredible adhesion. It will stick to just about anything.
- Dried film is impervious to odors – Two or more coats of shellac will seal in any kind of odor in any type of porous surface.
- Stain sealer – Shellac is arguably the world’s most effective stain and knot sealer (another reason why we use it to make B-I-N® Primer-Sealer).
- Easy to touch up and recoat – Unlike other finishes shellac can be easily touched up if it is scratched or worn; a new coat of shellac melts itself into the existing coat.
- Easy to clean up or remove – Shellac is dissolved by household ammonia as well as alcohol, making it very easy to clean brushes and other tools.
So that last point is one of the reasons why shellac eventually fell out of favour. While a good shellac finish is actually quite water resistant, it is easily dissolved by alcohol or ammonia. So spilling your scotch or setting the Windex bottle down on a nicely french polished table can be a disaster. Now that I think of it, I wonder if all those doilies that infested the homes of my childhood were actually hiding something…
Anyway, despite its wonderful properties shellac use eventually waned and it was replaced by lacquers and varnishes that could be more efficiently applied in mass production settings.
Why I Like Shellac
Until recently, my only experience with shellac was having used it as a sanding sealer way back in high school shop class, and a later humiliating attempt at French polishing. Recently though, there seems to be a bit of a rebirth of shellac happening particularly among woodworkers and instrument builders. You can find a lot of good information on how to mix it and use it for all sorts of applications. The reasons why I recently became interested are:
- I don’t like using mineral spirit finishes. I don’t mind the results, just the smell. My workshop is in my basement and it’s part of my home so I don’t want finishing fumes getting all through the house. Consequently, I opt for a water based finish if it will work. Although shellac is alcohol based, it flashes off very quickly, drastically reducing the time I need to ventilate my shop while finishing.
- Call me old school, but water based clear finishes don’t add enough life to the wood. I miss those tawny, varnish-like tints that you get using oil based products. The shellac helps add some of that back.
By using one or two coats of dewaxed shellac as a seal coat followed by a water-borne polyurethane, I’ve found I can get a hard and durable finish that looks much more like a traditional finish and is less ‘plasticky’ looking than a clear water-borne polyurethane by itself. To my eye at least, it also seems to even out any blotchiness that can occur in highly figured woods and it adds some depth, richness, and clarity to the overall finish. I even learned a new word for this: chatoyance. Fun party tip: Try holding up your wine glass to the light and saying, “This Pinot has an extraordinary chatoyance!” No, it has nothing to do with wine, but it will rattle any wine snobs within earshot to think there might be a silly wine word they don’t know!
Chatoyance actually describes the way that light disperses through certain gemstones and other materials producing a ‘cat’s-eye’ reflection. It’s also used to describe the 3-dimensional appearance of wood grains. The particular optical properties of shellac seem to bring this out even when it is buried underneath a few coats of clear poly. It’s hard to capture this effect in a photograph but here’s one of a red alder vanity drawer. I applied a shellac seal coat and then three coats of Minwax Water-Based Oil-Modified Polyurethane (semi-gloss):
One thing I really like about this oil modified polyurethane is it’s ultra-low odour. The oil in it also adds a bit of colour. However, like most water-borne finishes it can be tricky to apply, particularly on fiddly bits like face frames. I did find some crazy expensive synthetic ‘badger hair’ brushes from Gramercy Tools (available from Lee Valley) that are specially made for water based finishes. They seem to do the trick, but you sure want to remember to clean them after use! For the shellac base coat, you can use just about any old brush. As a bonus, you don’t even have to clean it well because you can just melt the shellac again with alcohol. That’s the beauty of shellac, it can always be repaired since it is a reversible finish (of course this doesn’t help if you are only using it as a seal coat!). Almost all other finishes are a one-way chemical reaction that cannot be reversed. They will not melt with solvents once they have cured.
In test samples on red alder, I found that without a shellac base coat, the water in the poly finish would sometimes react with the tannins in the alder producing a much more reddish tone than what you see in the photo above. It’s like a red dye leaches out of the wood. While it doesn’t look bad, it just wasn’t the look I was after.
You might ask why I don’t just go with a 100% shellac finish? Well, I considered it, but the projects I’m working on currently are bathroom vanities and kitchen cupboards, both of which need a really durable coating. I’m hoping the polyurethane will achieve that. There are some people however, who swear by shellac even for these applications.
Mixing Proportions
I really can’t add anything new to the world of shellac knowledge but there is one thing that seems to be missing: a metric table for dissolving shellac flakes. All of the references I found for preparing shellac refer to one, two, or three pound ‘cuts’. The cut is the weight of shellac flakes you need to dissolve in one US gallon (128 oz) of denatured ethanol. Well, here in Canada our gallons are 160 ounces and all my weighing and measuring equipment (that I pilfer from the kitchen as needed) is in grams and millilitres. So here is my contribution to the great shellac fraternity: a table of metric mixing equivalents:
|
Shellac Mixing Chart |
||||||
|
Concentration (Cut) |
1/2 Lb |
1 Lb |
1.5 Lb |
2 Lb |
2.5 Lb |
3 Lb |
|
Metric (grams/liter) |
60 |
120 |
180 |
240 |
300 |
360 |
|
Alcohol Volume (ml) Shellac Flakes to add (grams) |
||||||
|
100 |
6 |
12 |
18 |
24 |
30 |
36 |
|
200 |
12 |
24 |
36 |
48 |
60 |
72 |
|
300 |
18 |
36 |
54 |
72 |
90 |
108 |
|
250 |
15 |
30 |
45 |
60 |
75 |
90 |
|
400 |
24 |
48 |
72 |
96 |
120 |
144 |
|
500 |
30 |
60 |
90 |
120 |
150 |
180 |
|
600 |
36 |
72 |
108 |
144 |
180 |
216 |
|
700 |
42 |
84 |
126 |
168 |
210 |
252 |
|
750 |
45 |
90 |
135 |
180 |
225 |
270 |
|
800 |
48 |
96 |
144 |
192 |
240 |
288 |
|
900 |
54 |
108 |
162 |
216 |
270 |
324 |
|
1000 |
60 |
120 |
180 |
240 |
300 |
360 |
Some Ethical Considerations
Here is an interesting video of how shellac is produced:
No denying it, shellac is produced in truly third world conditions. Depending on your perspective you may see this as either:
- Just another example of how we exploit poor indigenous peoples
- An ethnobotany success story where critical forests are being preserved through the harvest of sustainable non timber forest products.
While there are no doubt some issues with child labour and general working conditions, I think it’s great that some forests are being sustained by non timber forestry (of course, as a woodworker, I also like sustainable timber forestry too!). Anyway, like everything, I imagine things could be better, but not everyone can work in call centres or assembling iPhones (Or can they? Economics confounds me!).
I would be remiss if I did not mention that shellac is not appreciated by some animal rights advocates (I’m not kidding) and Vegans, who understandably do not like having their fruits, candies, and pharmaceuticals coated with bug poop. I do think the animal rights arguments are a bit of a stretch unless perhaps you are a strict Buddhist. Although it reportedly takes 300,000 lac bugs to produce one kilogram of shellac, most of them will live and die happy because making lac is a part of their short life cycle. While some die in the harvesting process, human husbandry protects the insect population by moving them from tree to tree to increase their numbers.
The Finish Line
As a wood finish, Shellac has had a mostly undeserved bad reputation, some of it promoted by companies selling alternative products. Today it is enjoying a minor renaissance and good shellac flakes are fairly easy to come by. For almost all applications you should get the dewaxed flakes.
I’m looking forward to trying it on some other projects as a complete finish. Maybe I’ll even try my hand at French polishing again now that there are some good YouTube tutorials that demystify the process.
Shellac naturally appeals to the do-it-yourself gene in me because I can make an excellent wood finish from scratch using nothing more than some bug poop and booze! Take that MacGyver!
Some additional resources:
Some companies that sell shellac flakes (there are lots more):