Introduction: Color + Finishes
For almost all my woodworking projects, I prefer to accent the grain of the wood rather than cover it up by painting. When I do paint, it's with a water based paint as it's easier to clean up (mistakes and after painting), and doesn't off-gas.
We've waited until the end of the class to talk about finishes, partly because there's no "right" answer when it comes to finishes, and everyone will have an opinion about how they want their piece to look. The aim here is to arm you with the knowledge of a few different types, and applications, then allow you to make your own mind up about what looks best on your woodworking project.
Step 1: Protection
Shop safety should be observed when using any stains or paint, even if the stain or paint isn't harmful to your skin the solvents used for cleanup might be. The easiest solution is to use protection in the form of disposable gloves.
There's the standard natural rubber latex gloves, the more durable and latex-free nitrile gloves, and the loose fitting and economical vinyl gloves (also latex-free). You'll find a glove to fit your preference, budget, and one that suits the application. Wearing something is better than nothing, and makes cleanup a breeze.
Unless you want to have a multicolored workbench, it's usually a good idea to cover your work area with some kind of paper to catch any drips. Don't forget to put on some eye protection, too. Stain or solvent in the eye is no fun.
Step 2: Application
These brushes have natural bristles set in a wood handle with epoxy. With a sturdy handle and rough bristles they can stand up to most solvents and are great for applying stains, epoxy, glue, or cleaning parts. They're more expensive than foam brushes but much less than paint brushes, so they're great for sticky applications where you'd want to dispose of the brush after.
Inexpensive and available in loads of sizes, these brushes apply a smooth and even coat, great for painting and finish coats. The head inside the foam is a plastic fin attached to a wood dowel, with repeated use the fin can warp or snap off the handle, the foam can also degrade after repeated use. These foam brushes are synthetic and may melt when used with solvents.
The same type of material used for T-shirts can be cut up into rags and used as a lint free rag. Lint free is important otherwise you'll be picking debris off the surface of your work with every wipe. Very inexpensive (free if you have old T-shirts!) these rags are great for applying stain, oils, or used for cleaning with a solvent. Rags can leave a "rustic" finish when used to apply (or wipe off) paint and may not be ideal for paint application.
Step 3: Types
If you've ever wandered into the paint and finishes section of a hardware store you'll know there's a very large selection out there to chose from. Here's a few of the most popular choices of topical treatments for wood, broken down loosely into colorants and clear finishes:
Wood stain is a colorant mixed suspended in a solvent - since stains are solvent-based they cure. The colorant can be a dye or pigment.
Pigments and dyes are largely used as colorants. The difference between the two is in the size of the particles. Dyes are microscopic crystals that dissolve in the vehicle and pigments are suspended in the vehicle and are much larger. Dyes will color very fine grained wood, like cherry or maple, which pigments will not. Those fine-grained woods have pores too small for pigments to attach themselves to. Pigments contain a binder to help attach themselves to the wood.
The type of stain will either accentuate or obscure the wood grain. Most commercial stains contain both dye and pigment and the degree to which they stain the appropriate wood is mostly dependent on the length of time they are left on the wood. Pigments, regardless of the suspension agent, will not give much color to very dense woods but will deeply color woods with large pores (e.g. pine). Dyes are translucent and pigments are opaque.
An older type of stain and high-gloss finish, mostly been replaced with newer synthetics but plenty of older furniture have a shellac finish that should only be touched-up with shellac. Usually sold as dry flakes which is dissolved in ethanol to make liquid shellac. Oh! It's also made from a Lac bug that's been ground up.
Paint is an application that will mostly obscure the grain of the wood when applied. Available in almost any color imaginable and can be applied with a roller, paintbrush, rag, or spray. Paints come either as a latex paint (acrylic), or oil. Latex paints are easier to clean up as they are water soluble and have a low odor. Oil paints are more durable and great for resisting water, but will require a solvent for clean up.
A hard and protective finish that is transparent, made from a drying oil, a resin, and a solvent. Typically glossy, but available as semi-gloss, varnish is applied over stains for a protective finish. Stain varnish is also available, which is a varnish with a dye added.
A type of synthetic abrasion-resistant and durable coating. This clear protective finish is great for protecting your wood from moisture and wear, and comes in different glossiness like matte, semi-gloss, and gloss. Some polyurethanes break down with UV exposure, so be mindful of what type you select.
Oils can be synthetic or natural, the two most popular are both vegetable oils: linseed oil and Tung oil. However, Tung oil has a tendency to yellow over time, which can make for an attractive finish if desired. Danish oil is another popular type of oil that's been mixed with a varnish.
A thick and sticky 2-part solution that finish that cures to a clear, very hard, and waterproof finish. Epoxy coatings are either sold as a 1:1 ratio where the resin and catalyst are poured together in equal parts, or in unequal portions that need to be measured or weighed before combining.
All epoxies have a "pot life" which the epoxy has to be used by before the curing process begins and the epoxy cannot be handled any longer and must be left to cure.
Step 4: Test
You may have found a color of stain or oil you like in the store but it can look very different depending on what wood it's applied to, sometimes there's a sample stick in the stain aisle to help you out and give you an idea.
Once you have a collection of colors in your own shop you can start your own stain stick (as seen above). Remember to number your samples to correspond with each can. Remember that stains will look different on different types of wood.
When you have a color you like, before you commit to covering your work test your finish on a hidden area of your work, like the back, underside, or inside. These "hidden" areas won't be seen by anyone and will give you an idea of the look of the stain. Allow the stain to dry before making the call, also try applying a second coat in the hidden area.
If there's no hidden area to your work you just need a scrap of the same type of wood (ideally a cut-off from the same section).
Step 5: Cure Vs Dry
A cured finish is not the same as a dried finish, as a finish takes longer to cure and can continue to do so even after the top of the finish seems dry.
"[curing is] a chemical process that takes significantly longer than drying. Some kinds of finish cure by evaporation of their solvent, and some cure by reacting with oxygen. Either way, the process continues after a film has formed on top." -source
A dry finish is exactly what you think it means, dry. Something to keep in mind is that some woods are more porous than others and the surface might be dry but there's small pools of the finish deep in the wood that's not yet dry. Most times it's not a big deal, but something to be mindful of if you're looking for a particular tint to your wood finish. Also, some thicker finishes take longer to dry than thinner ones.
Step 6: Food Safe?
All commercial finishes are food safe after they are cured. I'll amend this by saying that if you're planning on storing something very acidic perhaps try something other than your coated woodworking project. Also, coated finishes like polyurethane or epoxy aren't suitable for cutting boards as the finish can chip off and end up in your food, best to use an oil instead.
Though any commercial finish is fine, sometimes it's easier to just buy the stuff that says right on the can "food safe".
If you want to keep things all natural there's loads of options like beeswax and mineral oil. Be mindful that most of the natural options will require frequent reapplication in order to keep protecting your work as it will rub off over time and with use.
It may be tempting to use a grocery store oil but I'd advise against this as cooking oils can go rancid over time, having rancid oil impregnated in your wood creation would be heartbreaking (and really gross). Best to opt for mineral oil, which is available everywhere, inexpensive, and as neutral as it comes.
Step 7: Standoffs + Drying
After applying your finish you'll need to let it dry (or cure). It's best to leave your work undisturbed in a constant temperature, as cold can prolong drying time and humid heat can make the finish go weird.
To allow air around all areas where finish is applied upturned screws make for great standoffs, the tip leaves minimal marking and finding matching screws is plentiful in most workshops.
Follow the directions of your finish when observing drying times, and in between coats. Typically, thicker finishes take longer to dry than thinner ones. When in doubt, wait overnight.
Step 8: Experimentation
Finishes can be a lot like alchemy, there's a few combinations that are known but through experimentation you'll find all kinds of combinations that work well together.
Though there's nothing wrong with store bought finishes many woodworkers mix their own "special sauce" for finishes that they've found over years of experimenting, so after you have a few types of stains and finishes try experimenting with different application methods, wait times, combinations of ingredients (be smart and safe, some chemicals don't work well together), and what sealer to use after a stain.
Step 9: Next Steps
Now that you're done with some of the fundamentals, keep your skills sharp by getting started on your next project!
Big or small, there's something you've probably been dying to make. If you're looking for more inspiration why not try some of these other woodworking projects, all can be made with the same tools we've been using in this class:
These projects use the same skills learned in this class and are great ways to use your woodworking knowledge in new ways. Get out into the shop while your keen skills are still fresh!
Get into the shop and make something awesome! Then, share your creation with everyone with an Instructable!