Getting Penetration with Spray Stain

      After switching from wiping stain to spray stain, a finisher asks for advice on working the material into fine cracks and crevices. December 31, 2012

Question
I am fairly new to spraying stain but so far am loving the switch over from wiping. I am spraying Sherwood stains mixed 3/1 with tolulene. I have found that there is a fine line on how much material to lay down. Too much and it will puddle, not enough and you feel like you are starving the wood. I am having trouble with crevices in the profiles not getting any stain. The flat services get plenty and the nooks and crannies seem to be missed. Are there any tricks to getting it all coated and it still being uniform?

Forum Responses
(Finishing Forum)
From contributor H:
It sounds as if you are getting a lot of bounce back from your spray. Try starting your atomizing pressure at 15 psi. It is thick, will reduce the bounce, and will get into the corners. Increase by 5 lbs to get the right look.



From contributor F:
I will assume that you are referring to SW dye concentrate. Any spray-only stain application is all about the gun and the person holding it. The gun with this application will achieve better results if it's a high quality HVLP. The higher the pressure the more of the halo effect that you will get in the profile. As far as pressure goes, that will depend on the gun. A certain pressure can never be applied to all guns across the board.

I have an HVLP that does fine at 12-14psi. A conventional may yield the same results at 25-30psi. That difference is huge in a spray stain. All that being said, set the gun to where it is atomizing at its peak and keep the gun perpendicular to the work at all times. None of those arc and pendulum techniques! If you try to intentionally spray the stain into the corners it will end up looking worse. The most forgiving spray stain that I have used is MLC'S Amazing stain. It hides overlaps very well and there is no thinning. It can also be used in between sealer/topcoats and as a shading additive up to10%.



From contributor J:
Contributor F - he is talking about cutting a wiping stain, and using it as a spray only stain.

To the original questioner: I spray them all the time, except I am using Valspar stains. I think your problem may be the solvent and the ratio. I use Naphtha mixed 5:1. I donít know how fast toluene is compared to naphtha, but I have experimented with standard thinner and found it flashed off to fast making application difficult. Also, by thinning more than three to one you get more control as you can build the color slower and more controlled.

Try 5:1 with naphtha, spray door edges lightly to avoid runs, and then quickly blow in the face to even out the color that blew by when spraying the edges. Now make a wet pass across the face. Spray so itís at the point where itís just about to pool on the surface. Hold the gun at an angle so the stain blows in to the crack where the panel meets the frame a little easier, maybe 10 or 15 degrees off vertical. Spray to the halfway point on the door, then rotate the door and keep going so you get the stain in the opposite panel/frame crack.

Give it a few minutes to dry, flip the door, and repeat starting with the edges again. You will never wipe a door again once you get this figured out. It just takes a little practice.



From contributor F:
To contributor J: SW also makes a Sherwood dye so that is why I asked. The toluene would be the only clue that it is a wipe stain. Toluene, naptha and VM and P naptha all work with alkyd based products but the naptha will be slower and therefore can add to the puddling problem because the stain takes too long to dry. Plus, at that ratio dark colors will be impossible to achieve without many coats and then it will become opaque without grain definition.

Chemically there is a bigger issue as well. Spray/wipe stains are meant to be wiped after application. The oils and resins are left on the woods surface if not wiped and then the coatings are expected to penetrate through them to get adhesion to the wood. If they penetrate you run the risk of coating migration, creating a hybrid coating to where the next coat doesn't know what it is sticking to and then wrinkling can occur as well. Just like oil and water don't mix nor does oil and lacquer, pre-cat, post-cat, conversion varnish and so on. I know what you may be thinking, "I've done this for years without any problems". You may have but sooner or later the odds are that it will bite really bad. If I'm doing a set of 40k cabinets that is just not the type of gamble that I am going to take. I'm not eating $40k especially when there are products that don't have to be thinned, (we rent solvent, we aren't able to keep something that evaporates so why add something if I don't have to?) and are chemically matched with the coatings that are going on top.



From contributor J:
To contributor F: Valspar actually makes a solvent to add to their wiping stains to convert them to spray only, itís just solvents. Iím in Canada and the solvent blend is not available. My Valspar rep told me to use Naphtha. If itís coming from the mfg I have to assume itís a legitimate practice.

I am assuming you have no experience with this technique. I too felt exactly as you did, until my chemical rep suggested it and I tried it. You want a little pooling, very little, and you donít want it to flash off too fast so it has a chance to soak in to the wood. This is why the fast acting solvents donít work as well. Itís not the same as spraying a dye/NGR.



From contributor F:
We don't see too much Valspar stains in our area just the coatings. They are not known for their stains in my opinion. As far as experience with that particular technique, no, but it sounds like you are having to do it out of necessity because of availability. Chemically it's not a fit to me. I have worked for three different coatings manufactures and a major distributor to the wood coatings industry and none have recommended this application. It's not all about the solvents. It also has to do with the carrier in the product as well. What is left on the wood is just as important as what got it there and evaporated.

The product I mentioned earlier (it isn't an NGR or a dye) if sprayed med. wet will yield a nice grain popping effect while multiple light coats will give the "multi piece door being one color" that women think that wood should be. Plus the other advantages that I mentioned with the ability to add after the seal coat in case parts are a little different in color or using as a shading additive. It also can be tinted to where extremely dark colors can be achieved with one-two passes. It can be used as a pre-stain conditioner or applied after a wipe stain to achieve a more uniform look.

Back to the original issue with halo - I don't try to intentionally spray into profile. I think that it makes things worse. If you have a chance to see a high ene flatline in use you will notice that the heads are tilted at an angle to get coverage on the edges as well as flat surfaces but not just to get into profile. Even these monsters still end up with a little halo especially after the panel starts to move. Kraftmade definitely has these issues.



From contributor R:
Toluene is not the ideal solvent for spraying stain or much of anything else. Toluene and Benzene are horribly toxic to liver cells among other things. I spray both dye and pigmented stains, but the real advantage comes from spraying dye or NGR (I use Mohawk) stains using MeOH, EtOH, Acetone, naptha or other evaporating solvent. I also will spray water-borne stains. In the case of waterborne and pigmented (wiping stains) it is just for the convenience of getting the material on the work. You still have to wipe it off. If you want control over the material in hard to get to areas, try using a touch-up gun with a fine tip and play with the pressure to get the atomization right. It can work. I also use a fast solvent and dilute quite a bit to get more control over color density and tone.


From the original questioner:
I will definitely try the 5/1 ratio with naptha and see what happens. The reason I was using the toluene was that my distributer doesn't carry the naptha. I may try getting from a hardware store.


From contributor J:
I should also mention you only want to use this with fast drying industrial type stains. Try not to use minwax or any of the other hour dry hardware store variety stuff.


From contributor M:
I have cut Sherwin-Williams oil based stains with lacquer thinner (for lack of a better alternative) 50/50 to make a very thin shading stain for darkening a previously wiped stain, but I would never do this for a kitchen. Only stand-alone items that I can reliably repeat in small numbers - small items I'm willing to risk a little adhesion issues. I've also done this with ML Campbell's wiping stains. Again, it's not a production level solution. If you are using a spray-only stain, I personally prefer spraying the stain on fairly lightly and then adding a shading dye to the topcoat so that you're getting depth/darkness in the same number of steps. Usually this looks quite lovely too.



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