The KZN North Coast Knife Makers Club was generously hosted by Allen Petrie of Greenhaus in Salt Rock (Shop 24, New Salt Rock Centre, 4391). If you are a woodworker and haven’t visited the store you are missing out as the store is stocked with a comprehensive range of products and some hard-to-find items.
He also runs workshops in the evenings for those who would like to learn how to make crates, picture frames or bigger furniture items like tables and benches. The topic follows on from a previous meeting by Bryon Briscoe of Woodoc where we covered a similar topic on finishing, but Allen was keen to share as much of his knowledge of woodworking and the club members are always keen to learn.
Selecting wood for maximum stability
As a solid wood furniture maker and bowl-turner, Allen has years of experience in selecting the best pieces of wood for each project. Knife handles are no exception in that care should be taken to ensure a stable cut of wood is chosen up front, as this will alleviate (not prevent) issues with warping and movement in the final product. As knifemakers we know that sending a knife to customers, who live in very different climates has its problems, but with this knowledge, we can select better quality wood to overcome these to a large extent.
In South Africa, the primary method used to process logs is plain/flat slabbing due to the ease and cost-effectiveness and produces, which is great for the mills but for us, we have to navigate three distinct cuts (Quartersawn (90 degrees), Rift sawn (45 degrees) and Flat sawn) and determine how best to use them for our projects. Of these three the one we are after is the Quarter Sawn with its very straight rings as it is the most stable, ie less prone to cupping, expansion, and contraction.
Stabilizing wood certainly makes movement less of an issue but can never fully prevent the wood from moving at all. So as with many things in life, getting the basics right upfront will make your life easier down the line.
The problem with burls is that the grain runs in all directions so the shrinking and swelling are not along just one dimension. Consequently, they develop cracks as the wood movement fights within the block. As the wood fibres go in very different directions, treat burls like you would end grain, in that it’s very porous and needs throughout filling to get the best possible finish.
If buying wood and you’re unsure how green/young it is, you’re best off storing it for a period to let it acclimatize to your area and if still green, allow it to dry out. The traditional rule of thumb is to allow 1 year per inch of wood (air drying at home) and you’re aiming for a moisture content of between 10-12 percent in general.
Pro Tip: You can dry wood out in an oven at 100 degrees Celcius if in a pinch. If you’re worried about the wood cracking or warping, place a small bowl of water in the oven as well.
Recommended: The Woodshop Widget
The Woodshop Widget app (iOS) is also one of the very useful apps if your work involves a lot of wood. The app gives you an estimate of how boards of different species of wood might grow or shrink under different conditions.
Other than that, the app also contains tools like species comparison, a board volume calculator, unit conversion aids. The app also contains a list of densities of around 200 types of wood, which is quite useful for a woodworker
What is Shellac and how to apply it?
Shellac is derived from a resin that is secreted from the female lac bug, an insect native to certain forests in south-east Asia (India and Thailand). This insect secretion is scraped from the bark of trees and, when processed, takes the form of small, light-brown or orange flakes.
To make an applicable woodworking finish, these flakes are mixed with alcohol (clear mentholated spirits). Woodworkers commonly use a two-pound-cut finish, which is to say a ratio of two pounds of shellac flakes per gallon of alcohol (or simply a ratio of 2:1). Other ratios are 3:1 for a thicker mix for end grain and open-cell woods or 1.5:1 for a lighter, thinner mix.
Shellac is an all-natural sealer and finish that’s non-toxic, fast-drying, and its this fast-drying quality makes it appropriate for where time is important. No special drying facilities are necessary, because it dries in a matter of minutes. Several coats may be built up within an hour, which for the knife maker, is a real time saver compared to other finishes that we use. If opting for a thicker cut (3:1) allow a bit more time between coats.
Shellac has wonderful blocking properties, better than any other finish. It blocks silicone contamination, which causes fish eye and residual wax extremely well. It also blocks the resin and very oily exotic woods, which can slow the drying of lacquer and varnish significantly.
Steps for a perfect shellac finish:
- Sand to 220-320grit. Sanding up past this can clog the pores of the wood, resulting in a dull and poor finish. It’s best to first apply your sanding sealer, in this case Shellac, and then polish the finish, if you’re going for a very glossy handle.
- Apply the shellac in multiple thin coats. The idea is to lay down a smooth, even application of shellac in a single long, even stroke. Then apply light coats of shellac with a moist, but not dripping, wet pad.
- The wood fibers with stiff and stand proud. Re-sand the raised nibs some the surface is smooth.
- Repeat steps 2 and 3, until you reach your preferred layer count.
- This direct application will result in a high-gloss finish. If a less glossy, satin finish is preferred, try buffing out the final coat with some 0000 steel wool.
If using de-waxed shellac (rather than waxed) you can use virtually any finish over the top of this, spirit, oil or even water-based finishes. With waxed shellac, you will need to a spirit or oil-based finish instead. Allen has used Woodoc Water-borne Floor over Shellac for knife handles, which resulted in a hard and durable finish.
Allen: I’ve learned that in retail, the finish is everything. An average piece finished well, will sell. A beautiful piece finished badly, will not. We take a lot of care when sanding. There are no shortcuts worth taking. – taken from The Woodworker Sessions #13
We wish to thank Allen Petrie (Greenhaus) for his time and willingness to pass on his knowledge to the club members. This blog post hopefully bears honest testimony to the discussions on the day, so that others may benefit as well.