How to Get the Ultimate Furniture Finish with Water Based Finishes – Part 2

How to Get the Ultimate Furniture Finish – Part 2.

By Marty Schlosser

In Part 1 of this article, I shared my first three “pro tips” for getting the ultimate furniture finish…

1. Understanding Objectives
2. Selecting Finishing Materials & Equipment
3. Preparation

Today, I’m going to share tips #4 through #7.

So, let’s pick things up after #3 – Preparation. After you have prepared your surface, prepared your spray finishing equipment, and prepared your environment for success, it’s time to move on to…

Pro Tip #4: Test Panels

This step is especially important when any new finishing products, techniques or finishing equipment are involved. Here are some things you should do:

– Prepare test panels using the exact same schedule and products as the actual piece. And follow the manufacturer’s recommendations regarding the number of coats as well as how thick each is supposed to be (check with your wet film gage). Ensure you also follow the recommended drying time between coats.

– Critically review your results; adjust the schedule, try different needle/nozzle/aircap sets (you do now that you can play around with different aircaps, right?), etc. as required. Re-accomplish test panels until you are confident you can consistently achieve the desired results.

Pro Tip #5: Apply Finish as per the Schedule

This is the part where you really get to see the results of the hard work you’ve invested up to this point. And this could make or break your ability to achieve the ultimate furniture finish.

Depending on your finishing project, you may have several different products to apply, including many of the following:

– Filler
– Colorants
– Shading and/or Toning
– Sealer
– Topcoat & Additives
– Polish & Wax

So, before you grab your spray gun, ensure you understand each of the steps of the schedule and proceed at a pace that is both efficient and effective.

I can’t tell you the number of times I’ve heard from others who lost a lot of time by having to rework a spoiled panel due to haste.

Here are some of things to be aware of, most of which is provided by the manufacturer, either printed on the tin or their product information webpage.

* Stirring. Ensure you properly stir all finish. In most cases this is done by hand using either a stir stick (I usually drill a few 10mm (3/8”) holes in my shop made wooden stir sticks to help them stir more efficiently) or a commercial finish mixer. Whatever method you use, refrain from shaking the tin or otherwise introducing air bubbles into the product.

* Straining. If you want the ultimate furniture finish, I highly recommend you strain any coatings you put into your spray gun – even those equipped with built-in strainers such as 3M’s PPS system.

The reason for this is simple: if your spray gun or built-in strainer becomes clogged, you’ll have to take the time to clean it out before going on. And of course this usually happens at the most inconvenient time of the job! I should mention that I use reusable strainers in lieu of disposable paper strainers.

Oh, and don’t bother straining your leftover finish; simply pour it right back into the tin.

Strainers come in three general sizes:

– Super-fine, which has a 125 micron mesh, is used for most low-viscosity finishes (those less than 30 seconds with a Ford 4 cup, or 40 seconds with a Zahn 2 cup)

– Fine, with its 280 micron mesh, is good for medium-viscosity finishes (those between 30 – 40 seconds with a Ford 4 cup, or 40 – 50 seconds with a Zahn 2 cup)

-Medium, with a 400 micron mesh is for everything of higher viscosity.

* Don’t Overfill Your Cup. All cup formats, except special pressurized systems such as 3M’s PPS, should not be filled more than 3/4. Reason: the cup’s air vent (or pressure inlet) can become clogged by the finish that will be touching it whenever the gun is tilted – as it needs to be to spray at 90 degrees to the target area. If you’re consistently requiring greater volumes of finish to complete a job (or series of pieces) consider getting a pressure pot.

* Identify the Finish in the Cup with a Label. Like many finishers, I will often have more than one spray gun in use at any time, each loaded with a different finishing product. To keep from getting them mixed up, I label the cup of each with a short piece of masking tape upon which I’ve printed the name of the finishing product. Now how’s that for an inexpensive, yet effective tip?

* Wet Film Thickness. This is the thickness of each coat as recommended by the finish manufacturer. Because film thickness can affect the leveling out, bonding and the curing process, it’s important that you follow the manufacturer’s thickness recommendation. Until you’ve become familiar with what the correct wet film thickness looks like right after being sprayed, you need to figure it out by using a wet film gage.

* Drying time between Coats. Similar to film thickness, manufacturers will provide recommendations for how long you need to wait before applying the next coat of finish. Although this can sometimes be reduced somewhat by the use of a fan set to medium speed, until you’re familiar with the finish’s nuances, stick with the recommended timing.

* Number of Coats. Again, manufacturers will usually provide this information on the tin or website. Follow such guidance.

* Spraying Technique. As a general rule for the ultimate furniture finish, aim your spray gun so the finish strikes the surface at 90 degrees on all planes, and hold that position as you advance across the surface. (If your piece has curved sections, change the angles to conform with the curve).

Start spraying before your spray gun reaches the edge of the piece and don’t stop until you’re beyond the other edge. Trigger off at the end of each pass.

Ensure you overlap each pass by 50% and try to maintain a consistent speed as you move along the surface to provide for a more consistent wet film thickness. You will be more successful if you follow these widely accepted spray finishing techniques.

* Control Overspray and Masking Off. Develop an awareness of where any overspray may go (even HVLP systems have a certain degree of it) and plan your spraying “route” along any piece accordingly. Remember to spray the most noticeable sections last to limit any possibility of overspray getting there.

I usually limit assembly to the greatest extent prior to finishing (e.g. where possible, hold off on fastening the back off a cabinet until the finishing is done), and most especially small cabinets where maneuvering a spray gun is challenging.

Note: 3M’s PPS is a great boon to those whose work consistently includes confined area finishing.

* Clean your Spray Gun. Without sounding alarmist, few things will botch a job more readily than a dirty, clogged spray gun. Here’s my three Levels of Spray Gun Cleaning, together with when to perform them, and how:

Level 1 Cleaning. Whenever you change out one finishing product within the same family (i.e. both are water based or solvent based or spirit based), using the same spray gun; or when you’ll be taking a few hours break, perform what I call a Level 1 cleaning: replace the finish in the cup with solvent and spray until only clear solvent exits.

Level 2 Cleaning. If changing needle/nozzle or aircaps, perform a Level 2 cleaning: Level 1 plus removing the aircap, needle and nozzle to thoroughly clean them as well as the spray gun fluid passage. Dry everything, then reassemble the spray gun.

Level 3 Cleaning. Then, if you are either changing out your finishing product to another of a different family (i.e. water based to solvent based or spirit based of any combination thereof) perform a Level 3 cleaning: Level 2 plus a thorough flushing out with denatured alcohol.

For My Example Project  (my spouse’s craft room with its Murphy bed and cabinetry) a special staining step was needed.

The 14 panels involved in my project were designed to be inset 11mm (approximately ½”) into their cope and stick jointed framing.

This required the inset sections to be stained prior to assembly. (Note: Foregoing this could cause the resultant unstained part of the panel tongue to show whenever seasonal shrinkage occurs).

What I did in this case was to set the pattern on my spray gun to a circular shape and use it as a poor-man’s airbrush for staining the tongue itself – and just slightly beyond.

In that way, once the partially stained panel was assembled into the frame and the entire framed panel stained as a whole, the visible tongue area would appear the same as the rest of the panel instead of showing up as a lighter area.

Another tip is to mask off any areas you don’t want to the finishing product to land on. For this I’ve found that Norton Paint Check is one of the best masking paper products on the market.

Pro Tip #6: Dealing with Runs & other Challenges

Mistakes happen; here’s some common ones and what to do about them:

– You’re spraying a vertical surface (think: cabinet gables) and you get a run. Let it dry, then scrape it off with a razor blade if it’s small… or sand it off if it isn’t.  Apply another coat to the entire surface, or, if you’re experienced, you may be able to get by using my spot repair method (explained below: “An insect has landed…”).

-You’ve sprayed too thin a coat and the surface feels gritty (or it may be the dreaded orange peel). Let it dry then sand with P400 grit sandpaper and spray another coat – respecting the recommended wet film thickness. You may have to spray an additional coat, depending on how it feels.

-An insect (or hair… for those of you who still have some) has landed on your freshly sprayed coat. If you see it right away, pick it off using a pair of tweezers and feather on what I call a spot repair coat (while sweeping your gun just off the target area, start squeezing your gun’s trigger to deliver the finish where needed, and once past the target area, continue sweeping it away while you slowly release the trigger.

-You’ve sprayed too many coats over too short a timeframe and the finish is “blued.” Leave it be for an hour or two and with any luck the finish will clear itself. If not, then you’ll have to sand or scrape away the finish and start over. Sorry!

-You’ve mistakenly sanded through your sanding sealer and stain coats, all the way to bare wood. If you’re lucky and the sand-through is in one small area along an edge, you may be able re-color the area with a touch-up pen… but odds are you’ll have to reapply the stain to the area.

In most cases I use my touch-up gun as an airbrush to blend stain into the area. This process is much akin to toning. It requires patience and, in most cases, a few very, very light coats to be successful.

Once fully dried, apply another few coats of sanding sealer, re-sand and continue with your finishing schedule.

-You’ve mistakenly picked up the wrong spray gun and applied a coat (or two…) of the wrong finish. Depending on the finish you’ll most likely have to wait until the finish has dried before sanding it off and starting over again.

Pro Tip #7: Documenting Process & Results

I keep a binder in my spray finishing cart, which I use to document every finishing project I undertake.

I allocate one page for each separate project, and detail every aspect of the job: finishing products and equipment used; the finishing schedule; and the results.

I have used this information on more jobs than you could possibly imagine and have found it most useful when a client returns, asking me to craft them another of the same piece, or to refinish a similar piece they wish placed in the same room, etc. The notes go so far as to detail any special techniques and equipment settings.

In the same binder, I also store my finishing equipment manuals as well as printed copies of finish manufacturer’s technical data sheets and SDS information. If you haven’t already done so, I highly recommend you set up a similar system.

I hope these tips will help you achieve the ultimate furniture finish on all your projects.

What tips, ideas or experiences do you have in achieving the ultimate furniture finish?

Please share your thoughts or read what others are saying in the comments section below.