Production Friendly Finishing

[The Grand Wazzoo]

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On Saturday, March 14, 2009 1:13:46 AM UTC-4, The Grand Wazzoo wrote:

Production Friendly Finishing


I attended a finishing workshop that was unlike any other finishing workshop that I had been to. It was called "Production Friendly Finishing". The materials and techniques that were talked about in the seminar were all based on the product offerings from Akzo Nobel, the largest manufacturer of chemical coatings in America, and possibly the world. It was not really a sales pitch meeting, but since the instructor is an Akzo Nobel tech, the finish discussions were in the
context of the Akzo Nobel product line.


I took notes at this seminar. The notes are more or less in the order in which they were given. As you read through, you might notice a disjointed pattern or a jumping of one topic to another. As the seminar was given, the instructor would entertain questions and comments from the attendees.

 

Production Friendly Finishing Seminar Notes

The seminar focused on only a few types of coatings ("finish systems") and what they are made of:


          - lacquer
          - precatalyzed lacquer
          - post-catalyzed lacquer
          - conversion varnish


Each coating type is called a "finish system". Each finish system has limits as to how much layering of colors and coats you can do. This layering is called "multi-color steps" or "multi-layered colors" and they are part of a finish schedule called "multi-step finishing".

Layered on colors give you depth and consistency all over, as well as clarity.

-Catalyzed (and for these purposes precatalyzed coatings fall into this same category) finish systems differ from nitrocellulose lacquer finish systems in one way because not every coat melts into one another. A continuous film is not formed by a catalyzed finish because there is
often just a mechanical bond holding layers of finish to one another. Adhesion is a big concern in developing a finish schedule using a catalyzed finish system.

You cannot do the same extensive layering of colorcoats and finish with catalyzed coatings as you can with furniture grade lacquer-type coatings because each coat underneath is not going to redissolve and knit together the way that they do with nitrocellulose lacquer systems.

In the furniture industry, they layer one coat after another, coat after coat. They sandwich in color coats with washcoats and sealer coats and do quite a lot of color layering. This is just not the case with the conversion coatings. Conversion coatings have parameters that do not
allow the almost endless layering of colors, all with coats of finish that knit together nicely to form a continuous film of finish.

-Catalyzed finish schedules are usually as rudimentary as staining, sealing, topcoating. This is not done for simplicity, but as described above, there are limitations in trying to get a catalyzed finish system to have the look of factory-finished furniture (which has the big advantage of being lacquer-based)

-Conversion varnish is a crosslinking finish system. You have two [or more] resins that bond together during the catalyzation process. The catalyst links the two resins together. This is the "crosslinking" that makes these finishes so tough, durable, and chemically resistant.
Without the presence of the catalyst, the finish may never cure [properly].

-Catalyzed lacquer formulations are mixtures of lacquer and varnish [resins] which link together because the catalyst has been added.

-Precatalyzed lacquer has some of the drying characteristics of lacquer and some of the curing characteristics of varnish (as in conversion varnish, not the varnish that is reduced with mineral
spirits). Precatalyzed lacquer is considered a "convenient system" because you end up with a durable film close to the properties of a conversion finish and you do not have to add catalyst or worry about pot life or "sweating time". Sweat time is  the amount of time you are supposed to wait (according to each manufacturer’s tech sheet for their coatings if they require a sweat time) after you mix in the catalyst to your finish but before you can actually start using/spraying the
finish. When you use a precatalyzed lacquer, it handles like lacquer and cures
to a much more durable film.

Not all precatalyzed lacquers are the same. The variations in performance of one brand to another is accounted for by the fact that if you dump the tiniest percentage of varnish into your lacquer -- as a formulation, not that we should become cooks in the kitchen creating our own brews because these will NOT work. Then add a weak catalyst to your formulation. And also add in some special additives which prevent the catalyst from kicking (crosslinking) until those additives evaporate out of the film (that means that only until after you open the can and apply the finish). So this minute quantity of varnish is enough that you can market your product as precatalyzed lacquer. So some manufacturers’ precatalyzed lacquers may be quite weak compared to post-catalyzed systems, and they may be only a little more durable than conventional lacquer. You should test each coating with a variety of performance tests to see what you have and what you are giving your customers.

- Every varnish system has the potential to lift and wrinkle the coats underneath. You may have to push the window quite far to get the coating to do that, but it is possible that these coatings can do that. Along with your project that you are coating, Akzo Nobel recommends that you have available a test panel that you are finishing with the same steps. That way you can see with each application of the coating if something bad is happening. It is easier to waste a test panel than it is to wash down a cabinet and start all over.

-   Finish systems that are promoted as self-sealing systems do not need any sealer coats (vinyl sealer since it is obvious that stearated sealers do not fit in with these systems at all). Some self-sealing finish systems still allow for the use of vinyl sealers as part of the finish schedule. Some self-sealing systems do not tolerate any sealer, and their spec sheets would be clear in specifying that stipulation.

-   Wood preparation is an important preliminary part of your finishing. Sand your surfaces to 120 to 180 (in sequence, starting with your most abrasive grit first), depending on the wood species. If you sand uniformly well, you will do a lot to control the stain penetration. This will help you with appearance issues of depth and definition.

The experiences of the seminar instructor are that sanding to 150 grit on a random orbit sander (like the Dynabrade) is equivalent to hand sanding with 180 grit sandpaper.

Cherry can be sanded to 150 grit. Maple should not be sanded to more than 180 grit. (No one asked if these suggestions were meant to apply to machine sanding or hand sanding).

- Pre-stains can be made from NGR’s. They are reduced so that there
are no overlapping problems (they are sprayed on).They are used most to create a pleasing wood "under tone". The color strength depends on the finish schedule, as does the actual color. These stains are the first coloring step in the layered color finish. Used with a good wiping stain, they add depth and character to a color, as well as uniforming properties. Since they are alcohol-reduced, there is almost no dry time to contend with. There is also no film build. They are not applied to the wood so as to flood the wood with material. Spraying them is equivalent to applying hair spray, or maybe a little wetter.

-   If you are spraying a complex shape, use weaker cut pre-stains and washcoats to insure the consistency of the application to the surfaces.
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-   Veneers take stains darker than do the solid wood portions. It appears as if the stains soak in more or penetrate the surfaces more. Some manufacturers recommend that you sand the veneer portions one grit finer than you sand solid wood portions.

Another suggestion for veneer vs. solid wood is to cut the wiping stains so they do not bite or penetrate into the veneer as much as they do into the solid wood.

- When mixing (intermixing) stains to come up with a nice wiping stain color, if you are trying to do a brown, a touch of violet seems to add a nice cast to the brown.

 

-   Lacquer can tolerate a certain amount of stain dumped into it even though most stains and lacquer are not fully compatible. The mineral spirits and similar solvents in many stains can cause the lacquer resins to "kick out of solution" if there is too much of them added. That’s why you can only add so much.

When you spray lacquer over a wiping stain that is not completely dry, you get a white haze that develops. This is the lacquer that has been kicked out of solution by the presence of those certain solvents. The fix is to spray on some retarder or often another coat of lacquer.

Conversion systems tolerate very little when it comes to incompatibilities. That is why it is so important to follow the manufacturers’ recommendations and pay attention to their tech sheets that they write for each finish.

- Dye stains need to be 100% acid compatible. Otherwise they could color shift when used as part of a catalyzed (and precatalyzed) finish. The colors that they are supposed to create could actually "flip".

Can you make a toner with conversion varnish? Many suppliers have colored conversion varnishes (they are like paints). Start with these and reduce them as needed for the opacity that you want. Mix in appropriate colorants as needed to make or shift a color that you need. Pay attention to how much you add so as not to throw the chemistry of the coating off by adding too much colorant. I would need to see what the available colors are in these catalyzed colored finishes, but I think that I have follow-up questions about making toners. Each manufacturer is different in what you can and cannot do with their finishes. And the theme of this seminar seems to have been that you should know what the limitations or parameters are of the coatings that you are using. Sometimes or often, the bad effect of being a maverick finisher are not so visible and not so obvious. It’s like having an aunt who lives to 96 years old. But if she ate more broccoli in her lifetime maybe she would have lived to 98. Or maybe she would have been more comfortable after she reached 92. Getting the optimum performance and use out of your finish means using them how they were designed to be used and applying them in the way that they were designed to be applied.

- Sometimes a wiping stain will not take so well on wood (maple is one example where this happens). Rather than fight, you might want to open the wood pores. This is called "grain popping" (not the same as bringing out the chatoyancy of the wood). A grain pop is made by mixing alcohol and water, and then misting it on the wood.

-   Conversion varnish finish schedules use a simplified series of finishing steps, as has been said. The dye stain is applied (the pre-stain). Then right on top of that the wiping stain is applied.
There are limits to these coatings -- as has also been said -- and you have to watch the film build. That is why there is often no washcoat to separate the two colorings (as you would often have in a lacquer finish schedule).

-   The Akzo Nobel glazes that they make have long dwell times. They sit wet for at least four hours before you can topcoat them (sometimes overnight waiting is advised). There is a reason for this long dwell time and it makes a lot of sense to me. Workability. You can apply these glazes and manipulate them and work them without having to worry about them starting to set up while you are trying to manipulate them (and this sure has happened to me often). You just have to plan your project accordingly to accommodate that four hour minimum. These glazes never fully dry/cure. They are specially suited to being part of an Akzo Nobelconversion finish schedule so as not to cause problems with adhesion between coats.

-   If you use the wrong [type of] glaze then the topcoat may not bond with the sealer. The glaze coat would then be like layering a sheet of wax paper in between coats. You need intercoat adhesion, whether it is chemical adhesion or mechanical adhesion.

-   The complex nature of these conversion coatings means that your wiping stains should be alkyd-based. Alkyd is a resin. Way back the issue of linseed oil-based stains was discussed as well as stains that use other binders that may not be so well suited to having these complex coatings applied on top of them.

Also present in these alkyd-based stains are oils, colors, and inert pigments. Inert pigments are pigments that have no color value.

Inerts: Those inactive, extender pigments which have little or no hiding or tinting properties when wet with oil, varnish or similar materials, and which are chemically stable or inert.

-   If you cut a stain with reducer, it does not really make the stain lighter in color. Instead, to make a stain lighter in color is to cut the stain with its clear base stain. This clear base stain (from one manufacturer to the next) has the same balanced mix of solvents, oils and inerts as the stain itself, minus the color. Reducing the color intensity of a wiping stain by adding the clear stain base (instead of reducers) maintains the "chemistry" of the stain. That is to say, the chemical balance that the stain was formulated with is maintained. The stain is left with the same properties as before, but it now has a lighter coloring strength.

[Many stains that we see from various suppliers are not only intermixes of conventional colors, but many color choices are often reduced-intensity colors. The manufacturers use a method of varying the amount of clear stain base to an already manufactured color. What the manufacturer is doing is making the job of color selection easier by offering us tried and true popular intensities of conventional stain colors.]

- Here is a real good tip on how to check the color of a dye stain when we are mixing and/or reducing colors. Take a piece of white paper and did it into your mix (just like using litmus paper to check the pH of a liquid). The white paper will be accurate enough to show you the color and its intensity. It will not show you what everything will look like when this is sprayed onto your wood. But if you keep the paper (generally out of light) and mark on it what you mixed and what proportions you mixed them, then you can use this paper as a rough color standard when you have to mix up more of that dye stain. This paper will tell you if you have the proper concentration of color, and it is close enough to trust (do it a few times to get used to it and then you will become accustomed to this test).

-   When you are intermixing colors to make a custom blend, try to keep the color-mixing choices to three colors. Four to five colors should be the most. If you have a complex recipe for a certain color, then whenyou need to mix that color again it will be so much more difficult for you to “find” that color. If you keep the mixing formulas simple, then it is so much easier to get to your special color again and again. Keeping it simple makes repetition easier.


What tools do you need for specialized color matching?

- A scale is the most accurate way of measuring and blending in color.

* Measuring by volume using various mixing containers Beakers, pipettes and measuring cups are the most common methods that finishers employ. Volume measurement is accurate enough for most purposes. Be able tomeasure anything from a fraction of an ounce to more than a gallon.

* Some mixes need to be shaken and others need stirring. A paint shaker is good for a shop to have, as is some type of mechanical stirring devicethat can blend our mixes much better than we can do by hand.

* Keep extra supplies of the same substrate that you are using for finishing. Prepare that wood the same way that you will prepare the wood that you need to finish. These will be your sample boards and can be used to check your progress as you mix, make and apply color combinations.

* Paper and/or wood dip sticks (already discussed) are also handy for quick checks on color. But there is no substitute for an actual wood or substrate surface when you are trying for an exact duplication of color.

* Document what you do. Cooks do this with recipes. We are cooking up some funky looks so we should also be keeping records of how much and when we do each step. This makes it easier to duplicate the same custom coloring look each time after.


From an Akzo Nobel catalog:

    * Color Standards or Targets

When you achieve the color match you want, keep a panel and wet sample that is dated and protected. This will help you when you have to duplicate or reference your work.

    * Starting the Blend

Start by making a small batch, maybe a pint, to get an idea of what colorants to use. You can proceed with a larger batch with less chances of mistakes that can lead to waste.

    * Accuracy

      Accuracy and patience are always the best approaches to achieving and duplicating a color match.

    * Keep It Simple

The more colorants you add, the more difficult it is to duplicate. Try to reach your target using three tints or less. Some colors will require four or five different colorants and there is no other way to match your target. Accuracy in measuring is important regardless of how many [colorants] you used.


-   "High influence colors" like red or black which can quickly change a light stain or paint color.

-   We saw a Graco #600 N Spatter gun in use..This gun is no longer in production. Iwata bought the design from Graco, it's this dentical spatter/veiling gun that sells for about $450. Binks also makes a spatter gun, model #MSA-510-DEC decorator gun. The differtencre between the Binks and the Iwata is that the Iwata can also spray a disheling pattern (using a veiling lacquer).

Decorator guns (spatter guns) require a pressure feed pot. The reason is that they shoot at very low pressures, and that means that there is not enough air going through the gun to get the fluid up the tube in a siphon feed gun. The pressure pot keeps the fluid pressure consistent, and all you need is about 3 psi of atomizing air to get a nice, random and consistent spitting pattern.

Manufacturers usually use a lacquer based material to do their flyspecking. Even the manufacturers that are shooting conversion varnishes are using lacquer based spatter. The size and amount of the lacquer dots are not enough to cause an incompatibility reaction with any conversion varnish system.

Finally, the seminar seemed to turn to the issue of glazing and glazes. Glazes are a further coloring enhancement of a finished surface. You improve the depth of your woods when you isolate the colors with clearcoats (layer the colors between clearcoats).

However, the amount of layering that you can do with a catalyzed system is greatly limited in comparison to what you can do with conventional furniture grade lacquer.

# If you do not isolate the glazecoat from the wiping stain with some kind of clearcoat (or sealer) then the colors will run and blend instead of getting nicely layered.

As you are adding layers of color on the wood you are creating a look that has depth.

-  Your last "wipe" or manipulation of the glaze (prior to locking it in with a sealer or clearcoat) should be in the direction of the grain of the wood. Generally, when you use a glaze, you wipe it on and wipe it off. You use a brush to apply the glaze to the grooves and wipe up the excess so that it "hangs" in the grooves and crevices.

-   The Akzo Nobel glazes are special from the conventional glazes. They are made with the intention that they are going to be used in a finish system that does not interweave and knit itself into a continuous film. Adhesion is a big issue with these types of finishes that achieve adhesion by mechanical bond.

Also, the Akzo Nobel glazes (and the Valspar glazes, for that matter) are made in a slow setting vehicle. The wait time is a minimum of four hours before topcoating/sealing to lock in the glaze. Waiting overnight is also not out of the question. But the long dwell time is to allow the operator plenty of time to apply the glaze, manipulate the glaze, and inspect everywhere to insure that there is no glaze creating so much of a thickness that it can lead to adhesion problems (the topcoat will not be able to find the bottom layer of finish that it want s to bond with mechanically).


Glazes: A glaze is a type of wiping stain with a specific function. The oils, resins and solvents in a glaze are slow drying for extended workability over a sealed surface. This feature makes glazes an excellent highlight stain for added depth or antique finishes. This glaze system [the Akzo Nobel Glaze Mono Color #560 series] is designed for use with high performance catalyzed systems where mechanical bonding is an intricate part of the intercoat adhesion. When used properly glaze can add character to your color.


The glazes are set in an alkyd resin base, not a formulation based on linseed oil. Unless specified and formulated by a specific finish manufacturer, linseed oil based glazes can potentially act like layers of wax paper when used in catalyzed finish systems. Each finish manufacturer makes these complex finishes in ways that the limitations, working properties, and parameters of each finish are different. The coatings manufacturer is often specific about what their finishes tolerate. They do not spend resources (time and money) on what their coatings will NOT tolerate. So they make finish recommendations and they tell you what IS compatible and what IS tolerated by that specific finish. Then they write tech sheets that they expect us to read, follow, and understand.

- Sand the sealer coat with 240 grit. Then scuff with red Scotchbrite (woven nylon abrasive pad). Glaze and then topcoat the next day. You have to plan this out so that you apply the right steps when they need to be applied, like when something calls for it to be done the next day or the following morning.

-   When you offer a glaze coat in your finish schedule, that your prices should reflect 25% to 50% more than a less complicated finish. A finish with a nice glaze decoration is labor intensive. You are sometimes using a brush in an artful way, like an artist. You are creating brush strokes and doing so takes time, panel after panel, cabinet after cabinet.

-   A good quality china bristle brush is a good brush to use for glazing and getting soft, muted, brushed out decorated effects. The four hour open time for the Akzo Nobel glaze really does come in helpful.

-   Glaze coats done on paints (opaque coatings) take the most time. Every little things shows. Brush it on, blend in and mute, and brush again.

-   Beaded molding can add a lot of labor and work when using glazes. You have to be mindful of the accumulation of the glaze.

   Pad stains are similar to the pre-stains in that they are dye stains. A pad stain is a dye stain that is applied after your first top coat. Its purpose is to accentuate and/or highlight the grain patterns of the woods. These dye stains are often cut with some water to reduce the bite of the alcohol into the finish. They are applied with a rag folded up into a little triangle. More is less. They are not stark colors. Also, another pad dampened with alcohol is followed on the pad stain to mute its effects.

   Cowtails: One method discussed in the seminar was taking a piece of cheese cloth and rolling the two corners. Then you did them in some thinned lacquer so that they stiffen. Too hard is not ideal. You want the rolled corners stiff like the way that the cloth we use to apply stains gets after it has dried out a couple of days. Then you dip the ends in your cowtailing solution. Manufacturers use colored lacquer because this leaves less "ridging" and bumps (less texture to the cowtail). Then you swat the wood surface. Less is more, as it is with all decoration.


- The seminar concluded with a suggestion about developing coloring schedules for our work. Keep all the colors "in harmony" (not "harmonious colors as found on a color wheel). The color of the pre-stain should not be far from the color of the wiping stain. There are tonal differences, but they should not be on opposite ends of the color wheel. The reason is that if one coloring step were applied a little more unevenly then the next coloring step in some areas of a cabinet or surface, then the differences (when everything is completed) are much more difficult to pick up on. The differences in the uneven coloring become less stark because the coloring steps used colors that were close or "in harmony" with one another.

You get applications more and less in some areas because of the ways that we have to spray. By staying "in harmony" you can get away with more variation and you will still have an overall blend. This way, your look will "tolerate" more of an inconsistent application of various coloring steps. The color inconsistencies will blend in rather stand out as stark color differences.


Crackle Finishes with conversion varnish systems

Just before leaving (after the seminar), I noticed a sample door that had a crackle finish. It also had a conversion varnish topcoat. I was intrigued because I have never seen any products for creating these crackle finishes using catalyzed finish systems. In the case of this conversion varnish, the application technique is very tricky. You apply your stains  and finishes just as you would if you were doing a very simple crackle finish with a lacquer system (but instead you are using conversion varnish so everything is much less fancy because of the limitations already discussed). When you get to the topcoat that you want to crackle, you use any ordinary solvent crackle coating. But you must shoot it over the freshly applied conversion varnish within two minutes of shooting the conversion varnish. There is no room for error or misjudgment. You really have to have those moves down pat or the crackle will not look good at all. Then you wait until everything is dry to the touch, lightly sand to subdue or soften the crispness of the edges, and topcoat with conversion varnish.


My opinion is that on more projects we should be layering colors and separating those colors between coats of finish. There is more depth and beauty in this type of multi-step finishing. You also have more control over the color -- and that is just ONE reason that the big factories do  their multi-step finishing -- but you also end up with a project that looks "correct". Not in every case, but when you are called on to come up for a finish on some furniture that was made in the 1960’s or later,  and you need to recreate that look or modify it, this is where you begin.

And when you want to add more pizzazz to a catalyzed coating (and a precatalyzed coating) so that you can get the look that many retail kitchen and bath stores are offering their customers, now we know that there is a lot more involved in knowing what we cannot do with these complex coatings. The tradeoff of using these durable coatings is that they each have their own degree of limitations, and we need to respect what they are. We want to give our customers what they pay for, and we also want to do the best that we can and try to do an even better job the next day.