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Newsletter #166

Greeting from Bill Boxer, Sr. Vice President, Apollo Sprayers International, Inc            

The question that I get asked over and over is: Can you spray latex or emulsion paint with an HVLP? Yes. But here is what you need to know:

  • Latex paints differ in their formulation, composition and viscosity.
  • In the manufacturing process, many latex paints have coarse ground resins and pigments, unlike other coatings where the resins and pigments are finely ground.
  • The reason is that latex paint is generally made to be brushed, rolled or applied with airless spray technology rather than an air atomizing technology such as HVLP.
  • HVLP sprayers vary widely in the available nozzle pressure. Smaller, lower powered, less expensive HVLP turbine units do not have the pressure necessary to apply a generally acceptable smooth finish.
  • While you might get the paint to come out of the spray gun with a low powered HVLP system, application speed will be slow and the finished surface either wavy (orange peel) or coarse.
  • Thinning the paint is necessary to improve the ability of the equipment to atomize the paint better and the addition of a latex conditioner (Floetrol) will assist in helping the finish flow and level better.
  • How much you need to thin the product will depend on the size of the turbine unit, available pressure, and the quality of the paint selected. This will vary anywhere from 10% to 50%.
  • The downside of thinning latex paint is loss of sheen. A gloss sheen can become virtually a flat sheen with excessive thinning.
  • Slower drying and multiple applications are also issues.
  • On the brighter side, newer more powerful turbines (4 and 5 stage units) that put out much higher atomizing pressure allow less thinning (10% or less) and excellent results.

 

More from Susan Hudson, the remarkable finisher at
Black Dog Salvage (continued from October)
 

 

Aging New Wood


We often have to replace a board here and there on an old piece. Even though I will most likely be painting the piece, adding a wash, or glazing it, I want all the wood to resemble the original level of wear/color. In other words I don’t want you to be able to pick out the new boards. 

I use a number of tools to distress the actual wood, anything from chains, wire brushes, hammers, etc. Once I have the level of “wear” required I will use the following solution to weather the wood:
 
2 steel wool pads #000-0000
2 cups of Apple Cider Vinegar or White Distilled Vinegar 
Glass Jar with lid, like a mason jar
Coffee filter


Tear up the steel wool and place it in the glass container, add the vinegar. 

Cover and leave over night or for as long as a week, but check on it and “burp” the container by loosening the lid and then putting it back on. The longer you leave the steel wool in the vinegar the deeper the color of the patina, but in all honesty I have found one 24 hour period of soaking is usually enough time. Once you think it has “cooked” enough, remove the pieces of steel wool and filter the solution into a new jar using the coffee filter to catch and retain the bits and pieces of the steel wool. 

Cut yourself some sample boards of the same wood you wish to patina. Stir the solution and sample it on your boards. It will take an hour or two to discolor the wood. Don’t soak it, merely apply the solution with a brush and let it dry. Depending on the wood I will usually use two coats, sanding between coats to create lights and darks. Sometimes I will apply a glaze between coats to add extra dimension. You can also apply a wash of color over your final coat and then seal with your desired sealant.

Experimenting is the key to success with this finish. Because it is thin, it will run like water into areas you don’t want it to, so be careful to mask off any places where it is unwanted. Also be aware of the fact that vinegar is basically an acid and will mar some substances, finishes, counters, etc. permanently. I highly suggest working on a tarp or plastic backed canvas. The smell will dissipate. Memories of dying Easter eggs always come wafting forward in my mind when working with this solution. 

First photo is Vinegar Mixture on Oak: Vinegar mixture brush on rough oak. After two hours it turns a dark charcoal gray. Transformation takes a while depending on the weather. 

 

Second Photo: Vinegar solution brushed on rough oak. The left side has a blue paint wash over the solution to illustrate how you can change the outcome.

The right side, bottom right area has two coats of the vinegar solution, versus the lighter area at the top right. This illustrates how multiple coats can change the finish. 

 

Third photo: Vinegar solution on pine board. This photo shows the different tones and colors you can get depending on the wood you use. This is a piece of pine.

The top of the board has one coat of the solution; the side of the board is devoid of any finish, i.e. bare wood. 

 

 

 

 

  Just a bit more on upcycling. The above shelf unit is made from a 6 panel door by Black Dog Salvage. Great idea! 

Special of the Month, an Offer You Just Can't Refuse

 

Featured Article: Spray Finishing in a Small Shop - You Bet!  BY Carl Duguay 

If you work in a small shop you might think that spraying is out of the question. However, that's not the case. A knock-down spray booth will enable you to spray waterborne finishes easily and safely.

Use a Waterborne Finish

Waterborne finishes are ideal for the home shop because they don't give off as much volatile organic compounds (VOCs) as solvent-based finishes, so they're safer for your health. As well, they're practically odourless, easy to clean up, and they don't produce explosive vapours - so any fans or other ventilation equipment that you use in the vicinity of the spray booth don't have to be explosion proof.

Equally important, the current generation of waterborne finishes are just as durable, and produce as beautiful a finish, as the more traditional solvent-based finishes. There are a number of good quality waterborne top coats on the market, including General Finishes, and Safecoat.  

Choose an HVLP Turbine System

There are two basic types of spray systems – those that deliver air at high pressure (compressor driven spray guns) and those that use low pressure (HVLP systems). Compressor systems use siphon style spray guns, and operate on the 'venturi principle' - air passes over a narrow opening filled with the finish, sucking the finish out of the container, and depositing it on the work surface. This system tends to result in a great deal of overspray as a result of using turbulent high pressure (upwards of 50 PSI), low volume air to deliver the coating to the surface.

Alternatively, high volume low pressure systems (HVLP) have put professional quality spray application tools within reach of small shop owners and hobbyist woodworkers. Such systems are multi-stage turbines that deliver a large quantity of low-pressure air (10 PSI or less) to the spray gun. Some of this air is used to pressurize the cup containing the coating. When the trigger is pulled, this pressure forces the coating up a tube and into the air stream which then deposits it on the surface being sprayed.

Transfer rates with a conventional compressor driven gun can be as low as 20% with most of the coating being lost as overspray. With an HVLP system, it's possible to achieve transfer rates up to 90%. This means less of the coating will end up in the air as overspray, making this a much more efficient system to use in a small or home shop.

When looking for a HVLP, consider systems from the leading manufacturers.

Go Small

Space is at a premium in most home workshops and few are large enough to have sufficient room to set up a dedicated spray area. That doesn't mean you can't spray. But you do have to think, and work, small.

The key is to use a simple take-apart spray booth that you can quickly set up when needed, and easily disassemble for storage between uses. For large projects that won't conveniently fit into your booth, apply the spray finish to project components before you do your assembly.

You can make a spray booth out of any lightweight rigid material. Cardboard is a great choice because it's usually freely available and can be easily replaced when damaged. You could also use coreplast, which is available from most home centers and all sign shops. I've had great success using large appliance boxes. Usually I place them on a pair of 24" high shop-built sawhorses. I use a much more compact booth that sits on my workbench for small projects - jewellery boxes, display cases, drawer pulls, hand tools, and the like. If you chose to use a fan, set it on the workbench behind the spray booth, so that it vents away from the project you're spraying. Optionally, tape a furnace filter over the face of the fan to absorb any overspray.

Keep it Simple

To keep construction simple use duct tape. Cut the cardboard panels to the size you'll need for the front, back, and sides. The top and sides are held together with duct tape in a specific way, because the way you tape it together will determine how well it folds up. Lay the top face up on the shop floor and butt one of the sides up to it. Apply duct tape to the seam. Take the two pieces and fold them together, face-to-face, with the duct tape in the center. With the two pieces closed, apply tape to the seam from the outside of the joint. This will allow the two pieces to fold up in one direction only. Repeat the previous steps to attach the other side.

Play it Safe

Even though waterborne finishes are much safer than solvent based finishes, it's still a good idea to wear a respirator when spraying. Just as important, keep your equipment clean, especially the jet nozzles on the gun. When you're only doing a small amount of spraying there may be a temptation to 'clean it the next time'. I've made that mistake, and wouldn't want to repeat it. Most of the time, problems with spraying come down to technique. If you've not done it before, take the time to practice using the equipment. Understanding how to use an HVLP system isn't complicated - developing proficiency in using the gun does take time, and practice.  But, if you're looking for the optimal finish, then the investment of money and time is well worth it.

Finishing Tip: Wetting to Predict Blotching

You can usually get a pretty good idea whether or not the wood you are using will blotch when a stain or finish is applied by wetting the wood.

You can use any liquid, but water will raise the grain causing you to have to sand more. Mineral spirits (paint thinner) works well except if you intend to apply a water-based finish. Some residue oiliness may remain and cause the finish to fish eye—that is, bunch up into ridges rather than level out.

Denatured alcohol would be better for this situation because it will totally evaporate. But it evaporates quickly, so you don’t have much time to judge the potential for blotching.

One possible solution would be to wipe with mineral spirits to provide more time, then remove the oily residue by wiping with denatured alcohol.

Take a Break and Have Some Fun

See how many words you can find. Look for words horizontally and vertically. You can print this page, including the puzzle, work offline, and then highlight words as you find them. 

 

More Good Ideas

       

20 of 20 words were placed into the puzzle.