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Monday, December 15, 2014

Woodworking Finishing Tips

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By Jim Hingst

Soft woods, such as pine, are prone to blotchiness, in which some areas of the wood absorb more stain and darken compared to other areas. To produce a uniform finish, follow Jim Hingst's woodworking finishing tips.

Filling Cracks in Wood with Epoxy


Some wood has imperfections, such as cracks or  knots, that should be filled before sanding. The easiest way to fill these holes is to run down to your local hardware store and buy a can of wood putty. It is the simplest solution, but probably not the best. The reason is that wood putty can fall out over time. A much better solution is to fill the cracks in the wood with epoxy colored with pigment. It takes a little more effort, but it is much more effective. Here’s why. Epoxy penetrates the pores of the wood and holds on tighter. The epoxy that you use as an alternative to the wood putty is the same epoxy that you use as an epoxy glue.

The process of filling cracks in wood with epoxy is not difficult. You do need to be prepared to work fast, however, because epoxy has a limited working time. The first step in working with epoxy is to assemble everything that you need in one place before you get started.

The next step may or may not be required. Check the wood for your project piece. If the crack goes all the way through the wood, you will need to do some taping. 3M Blue Painters Tape will work.  What works even better is clear plastic packaging tape.

There are a couple of ways to tape off a crack. One way is to tape the bottom of the wood and fill the crack from the top. That works for many woodworkers. Here’s the problem though. As epoxy cures, the chemical reaction creates carbon monoxide gas.  That means that bubbles form in the epoxy and float to the surface. To get rid of the bubbles, you can carefully heat the surface of the epoxy with a propane torch and that will burst your bubble. Another way is to tape the side of the board that will be exposed and fill the crack in the wood from the bottom. That way any bubbles float to the side of the board which will not be exposed. Both ways work. The choice is yours.

The next step is to mix the epoxy. If you use West System epoxy and use the metering mini pumps, mixing the correct ratio is easy. Measuring the resin and hardener in exact proportions is critical. Whatever you do, don’t be creative. Some people make the mistake of adding in a little extra hardener, thinking that they will aid the curing. It doesn’t work that way. In fact, adding more hardener creates problems with the epoxy curing completely.  

Also keep in mind that the proportions for mixing epoxy vary from product to product. Some brands require a 1:1 ratio. Other brands mix at a ratio of 5 parts of resin to 1 part of hardener. The lesson here is to always read the instructions and follow them to the letter.

For mixing epoxy, I use a plastic cup, such as a Solo cup. Make sure that you mix the ingredients thoroughly. For mixing I use the West System mixing plastic mixing sticks. These sticks are squared off which allows you to get into the corners of the cup.

Once you have mixed the epoxy, it is time to add the pigment powder. Many woodworkers will use either a black charcoal pigment or a dark brown pigment. You don’t need to add much. For you older readers, it’s like Brylcreem – a little dab will do you. As an alternative to pigment powder, you can also use a colorant such as Mixol.

If you are filling an imperfection on a vertical surface, you will need to mix in a filler to thicken it up.

When everything is thoroughly mixed, pour the mixture into the crack. A spoon works for this procedure. As I wrote earlier, bubbles will rise to the top. When they form, heat the epoxy with your torch. When the epoxy has dried completely, it is time for sanding.


Fill cracks in the wood putty or with colored epoxy

Sanding. 


Hand sanding produces much better results that using power equipment. The reason is that power sanders can leave marks in the wood. Use a sanding block, when sanding flat surfaces. Sand with the grain or at a very slight angle (3° to 5°). Work through the grits. If the surface is rough, begin sanding with 80 grit sandpaper. Subsequently, sand the wood with 100 grit, then 120 grit, 150 grit and finally 220 grit. For efficient sanding don’t skip grits.


When sanding flat surfaces,
use a sanding block.

Cleaning Off the Sanding Dust. 


If you have a shop vacuum, use it to remove as much sanding dust as possible. Then wipe the surface with a tack rag. While the wood may appear clean after wiping it down with the tack rag, the surface is still contaminated. The final step in cleaning is to wipe the wood with a clean cloth saturated with denatured alcohol. You will be amazed at all of the residue that the final wiping will pick up.



After applying the pre-stain
wood conditioner, allow it
to dry thoroughly for at least
24 hours before staining.

Applying Pre-stain Wood Conditioner. 


Using a foam brush or rag, apply a pre-stain wood conditioner to the surface of the wood. Wait 15 minutes and wipe off the excess. Regardless of what the manufacturer’s instructions are, allow the wood to dry for 24 hours. Two hours of drying time are insufficient.  If the conditioner has not dried completely, blotchiness may result. During the time that you are applying the pre-stain conditioner and while the conditioner is drying, maintain at least 65° F in your work area. Low temperature and high humidity will slow drying times. If the wood is extremely dry, it will suck up the conditioner like a sponge. A second coat may be required. Just before staining, brush on mineral spirits onto the surface of the wood. The application of the mineral spirits will limit the amount of stain that the wood will absorb, resulting in a more even application of the color and minimizing any blotchiness.



Mix gel stain thoroughly until
it has a creamy consistency,
before application.

Applying Stain. 


To minimize the chance of blotchiness, use a gel stain rather than a penetrating stain. A gel stain will stay on the surface of the wood, rather than being absorbed into the wood fibers. Stir the stain thoroughly until it is creamy smooth.

 A gel stain will also better cover up any of the areas where you have used wood putty. After applying the gel stain, wait three to five minutes before wiping the excess off. 

Touch Up. 


The nail holes, cracks and gouges that you have filled in with wood putty will not accept the stain as the surrounding wood will. In many cases, these areas will be noticeable, especially if you are using a penetrating stain. The solution is to do some touch up work. To disguise the wood putty patches you will need to rely on your artistic skills. First paint the grain lines using a dark earthtone color, such  as burnt umber. Then paint the surrounding areas with a lighter color.

Varnishing. 


Before varnishing, allow the stain to dry thoroughly. Generally, you must wait at least 24 hours before application. Low temperatures and high humidity can extend drying times.  The optimal temperature for applying varnish is between 70⁰F and 80⁰F or 21⁰C and 27⁰C.  This minimum temperature range is important for the flow out of the varnish. The proper temperature will also allow any bubbles to rise to the surface and disappear.  Never apply varnish, when the temperature is below 60⁰F or 16⁰C.

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About Jim Hingst: After fourteen years as Business Development Manager at RTape, Jim Hingst retired. He was involved in many facets of the company’s business, including marketing, sales, product development and technical service.

Hingst began his career 42 years ago in the graphic arts field creating and producing advertising and promotional materials for a large test equipment manufacturer.  Working for offset printers, large format screen printers, vinyl film manufacturers, and application tape companies, his experience included estimating, production planning, purchasing and production art, as well as sales and marketing. In his capacity as a salesman, Hingst was recognized with numerous sales achievement awards.

Drawing on his experience in production and as graphics installation subcontractor, Hingst provided the industry with practical advice, publishing more than 150 articles for  publications, such as  Signs Canada, SignCraft,  Signs of the Times, Screen Printing, Sign and Digital Graphics and  Sign Builder Illustrated. He also posted more than 485 stories on his blog (hingstssignpost.blogspot.com). In 2007 Hingst’s book, Vinyl Sign Techniques, was published.

Slides of Jim's Artwork

© 2015 Jim Hingst


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