Puddling of NGR Dyes Over a Sealer Washcoat

      A beginner with dyes gets advice on compatibility and application methods. March 3, 2010

I've just started working with dyes (and finishing in general). I've been spraying Solarlux NGR dye stains, and when I start to get a deep color, puddles form with drops of pigment in them. This is over a vinyl sealer wash coat (6% solids). Is my wash coat too thick or the dye too heavy? I tried using the reducer when spraying a whole piece and it just seemed to amplify the problem. Do dyes need a wash coat like wiping stains to control blotching?

I also tried mixing my own color dyes with methanol and Trans-tint. Similar results, less puddling and spotting, but blotchier overall. What about mixing with lacquer thinner instead of alcohol?

Is there a point where you can be putting too much dye on? Having a pretty deep dye color was key. The wiping stain and toner produce consistent results, but the dye seems to be where all the problems occur.

To get the color I wanted my finish schedule was:
1) 6% vinyl sealer wash coat
2) 320 sand
3) NGR dye
4) vinyl sealer
5) 220 sand
6) wiping stain
7) vinyl sealer with Trans-tint (toner?)
8) 320 sand
8) 2 coats conversion varnish

Seem like a lot of work but it was the only way I could match this cherry color the client needed - and it's dead on. After fumbling with the dyes enough, I thought to try the wiping stain after the sealer and that did the trick, but it doesn't seem like a good idea to have that in between coats. The dyes seem to really dull the grain of the wood and the wiping stain brings it back to life.

Can I tint the conversion varnish with Trans-tint instead of the sealer to save a step? Or is it better to keep all the color under sealer?

I just started spraying conversion varnish a few months ago and most of what I've learned I've read here. I need to achieve difficult dark colors and it seems like there are a million ways to do it. I have a few doors that got too dark from trying to fix the spotting and blotching. Are there any solutions you can use during the finishing process, or do you have to sand or strip and start over? This is after a big failed attempt at stripping a door with lacquer thinner halfway though the finish process and sanding almost clean. Color was oozing out of some pores, and sanding would only make this go away for a second or two.

Forum Responses
(Finishing Forum)
From contributor J:
First off, never spray a dye over a wash coat or seal coat unless it has some finish or sealer in the mix to act as a binder. This is why it puddles and spots. You may be able to get away with light coats this way if the dye is reduced with lacquer thinner or acetone, but in general it's not the preferred method.

Spray dyes directly onto the bare wood, reducing them with the appropriate solvent to make them weak enough that you are building your color in a number of coats rather than one heavy coat. Weaker concentrations of dye are more forgiving. You should spray each coat so that it is just barely wet; don't dry spray or flood it on.

Let each coat dry thoroughly before spraying the next. When sprayed properly on the bare wood, dyes will color and pop the grain in a way that wiping stains just can't duplicate, and if the color is built up slowly in multiple coats rather than flooding it on, it will not blotch.

You have to get used to judging your color, because the dyes dry so fast and look so different before and after sealing. This will come with practice.

Then apply your wash coat and wiping stain over the dye. I've done some finishes this way that don't get any wiping stain at all if they are to be glazed, as the glaze fills in the profiles that are hard to spray color into.

Trans-tints should be able to be reduced in just about any solvent, alcohol, lacquer thinner or acetone, but different solvent will have different drying and penetration properties. I like using a high quality, medium evaporating lacquer thinner.

I use Valspar Universal dye concentrates because they are virtually the same thing as Trans-tint at less than half the cost per ounce. The only drawback is you have to buy them by the gallon.

I would try adjusting your schedule as follows:
1. Spray reduced dye stain mix directly onto prep sanded wood; build color in multiple coats.
2. Vinyl sealer wash coat with a stronger mix, possibly up to 50%. A 6% mix is pretty weak and won't do much to prevent blotching.
3. Light scuff 320.
4. Stain or glaze. If a highlight glaze is not desired, use a fill glaze the same color as the dye.
5. If more color is desired, tone with mixing dye into finish.
6. Final scuff sand 320 and top coat.

From contributor G:
"...color was oozing out of some pores..."

What kind of wood are you using?

From the original questioner:
Cherry, and the spots it was coming from were random - not like a knot or something, just spots on the face of the frame in clusters.

When I spray the dye it usually comes out splotchy from the gun. I have a 1.1 tip on an Accuspray 19 gun with pressurized cup. Turning the air pressure up to 45 PSI evens it out but makes it spray dry. How long does it take between passes? It looks like it's drying instantly. I was making two light passes in each direction to even out the color, and the spray was probably on the dry side - but that was mainly because of how the gun sprayed it. On test surfaces it shoots an even line when not moving; when you start moving side to side is when it gets uneven.

I've never worked with glaze before, but know the time is coming soon to start. What are some recommendations for products?

From contributor J:
Some may disagree with me, but a 1.1 tip is too small to be useful for anything bigger than an airbrush. Even my touchup guns have a 1.4. A smaller tip restricts fluid flow and fan size. Increasing air pressure to compensate only creates more dry spray, although the pressurized cup on your Accuspray should help, but dye is so thin it should not need much cup pressure. My philosophy on tip sizes is that I would rather have to turn down a gun that has a big tip than try to crank up a gun with a small tip.

To put it in perspective, I use a 1.8 for almost everything, turning the fluid control down for thinner material when needed, and using it wide open for spraying thicker materials. I find that I rarely need to change tips. This approach may not work for everyone with every gun, but it works for me. Plus I get a kick out of seeing someone else try to spray with my gun and calling it a fire hose!

From contributor G:
As you observed, there are a million ways to get a deep color. Here is a suggestion for one of them:

1 – Finish sand 150

2 – NGR spray reduced with whatever until you need a minimum of 4 passes to get the color. More passes is okay. You want the NGR to be barely wet and dry quickly. If it puddles, that’s where you get the spots.

Your 1.1 tip should work. It won’t be as fast as the fire hose, but it is doable. Set your fluid feed wide open and the air pressure low enough so you get a soft spray. If you can’t get nice, even coats, use the gun I suggest in step #5.

To ensure consistency, have a step panel at hand to compare with.

3 – Vinyl sealer. If it’s too thin, it won’t prevent the wipe stain from lifting the NGR, but if it’s too high in solids, it will prevent the wipe stain from biting into the wood. You’ll have to experiment.

4 – Sand. It is not strictly necessary to sand at this point. Some say the wipe stain will bite in better without sanding the sealer. If you do sand, use a fine sanding sponge. Way faster than 220 paper and no cut-throughs.

5 – Wiping stain. Spray it on, wipe it off. Way fast. Your 1.1 tip won’t work for this. If you don’t have another gun around, get one of those $100 price range gravity guns. You will be surprised how much faster things go spraying and wiping.

6 – Vinyl sealer. If you try to save a step by tinting the CV, you will have to sand the CV between coats. Vinyl sealer sands much easier than CV.

7 – Two coats CV. If you stay inside the intercoat window, you won’t have to sand between coats. Good luck. Make samples.

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