Troubleshooting Blotchy Effects with a Water-Based Finishing Schedule

      Waterborne finishes make it tricky to get even tinting on some wood surfaces. Here, a finisher tries to zero in on a workable dye stain, barrier coat, and tinted topcoat system. December 28, 2007

Question
I'm trying to get into water based finishing, but the move has not been all that easy. I'm trying to use a schedule that would incorporate a dye coat to help unify the hardwood and plywood on my jobs (mostly kitchen cabinets), followed by a stain and topcoat with appropriate barrier coats.

My dye coat consists of Transtints in water, followed by a spit coat of Oxford water based shellac. I then apply a stain coat of Oxford clear water reducible linseed oil tinted with an appropriate Transtint color. Seal with another coat of shellac finish with 2-3 coats of Ultima spray lacquer.

I've had inconsistent staining. Gotten a lot of blotching and striping between the flitch cut maple veneer. Called Target and it was recommended that I start the schedule with a spit coat of 50/50 mix of their lacquer and water. The shellac will redissolve when it gets hit with the subsequent stain coat. After using the 50/50 spit coat, go through the dye, stain, barrier and top coats. Did that, not much better. Sanding was taken up to 220 and all disks were fresh. Ply was cleaned off between grits.

Now I'm in the trying this and trying that mode, and I've been assured that the schedule offered to me is working for everyone else. Is there anyone achieving good results with a similar schedule in water base, and are there any opinions as to a brand that has good technical support and reps that can actually swing by your shop and talk knowledgably about their water based systems? I would like to stick to a dye and stain schedule and not have to start getting into toning and glazing to achieve uniformity if possible. Two many variables. Find a close stain color, adjust the dye color.

Forum Responses
(Finishing Forum)
From contributor P:
When starting with a dye, I use the TransTint in water, sprayed and wiped. Seal with whatever Target water-based shellac, then gel stain, then shellac, then topcoat with the Target 9000. If I want to add more depth, then I'll tint the second shellac, spray an acrylic or use a prepared glaze. This works well for me, and I've done it on oak, German beech, alder, and birch, both ply and hardwood. I sand to 220, but on the birch especially, may go to 320. I spray the initial dye on with a squirt bottle, wiping as I go. This may not be the most professional manner, but it works.



From contributor W:
I've done it both ways, shellac as the pre-stain seal and a reduced WB lacquer as the pre-stain sealer - it depends on the species you are working with. I do a lot of cherry hard stock and veneers - the veneers are very blotchy, hard to control when using a dye stain, same with maple and birch. Here's my basic approach, but it does change from job to job based on the grade of the plywood veneer I'm working with.

Cherry:
- Sand 220 grit
- Prestain seal with 50% reduced
- Em8800 sealer or USL lacquer - 2 coats
- Lightly sand with 320 grit hand pad
- Apply Target WR Dye Stain (premix color or custom color using TransTint and WR Clear Base)
- Lock in dye stain with shellac sealer
- Proceed with topcoats

Some blotching may still telegraph through, but that's the nature of dye stains and blotchy woods. If you want to completely lock out any blotching, then a pigment stain over the pre-stain seal should be used... Or use a gel stain which also controls blotching but does not eliminate that problem 100%.



From the original questioner:
Thanks. I've found out the hard way that the schedule I used wouldn't work. Advice from the manufacturer was that the shellac spit coat will not lock in the dye coat and condition the subsequent wood stain, as it will redissolve with a subsequent coat of waterbase film. This, I'm told, is what is contributing to my flitch cut maple blotching. Not sure why the label on the can gives instruction for its use as a barrier coat or wood conditioner. I've tried it as the manufacturer suggested; spit coat of laquer/H20, dye, stain, barrier coat, top coat. The results were the same. Blotching in both the ply and solid wood.

I have distributors/reps from various companies of solvent based coatings on a hair trigger, willing to come out to my shop and demonstrate their product line and application. With the waterbased coatings, it seems as though the manufacturers are still small and can't employ that kind of sales and distribution network. Trying to reach some of them with technical questions is like getting a doctor on the phone in an HMO plan. I need a water based coatings manufacturer that has a good product line up (that can even handle birch and maple) and has good technical support. ML Campbell was great for this but I was told by my distributor that they pulled their water based stain package.



From contributor A:
You can also use Target's stain as a toner for the lacquer by adding it up to 6% to the top coat. Seal the piece of wood and spray on the toner for even colouration with no blotching on maple, birch, or cherry. This also works well on red oak if you don't want that heavy-in-the-pores look.

For a pre-stain I use the EM8800 sealer reduced 50% with water. Follow this by sanding it all back p320 and then apply the stain liberally. I only do this for high figure woods like curly maple or cherry.



From contributor C:
You can use some solvent-based stains with WB finishes. Mohawk has a line of solvent-based pigment wiping stains which work pretty well. I've used them under Target WB finishes with no problems. I've used a 1 lb cut of Zinsser Seal-Coat, followed by a solvent-based pigment wiping stain, followed by a coat of 1 lb. cut of Seal Coat, followed by several coats of WB finish. I've also applied the WB topcoat directly over the stain with good results. Let the pigment stain dry overnight. As always with any new finishing schedule, do an adhesion test: Use the finish schedule on some scrap material. In the case of WB finish, let it cure about 7 days, cut an X in the finish, apply tape, and peel it off. If the finish peels off, you'll have adhesion problems.


From contributor K:
I also have used Mohawk's 15 minute wiping stain with a coat of SealCoat under Target's with no problem. If you don't seal with shellac, I let the Mohawk dry two days just to be safe. I've also used Mohawk's Ultra Penetrating stain with good results. That can be topcoated sooner. I routinely use SealCoat as a barrier coat under Target (or any H20 finish).


From contributor B:
Don't give up on the Target line. Try alcohol-cut shellac (instead of the WB shellac) to lock in the stain. This way the dye won't bleed up into successive layers of waterbased finish. Or try their water based stain, which has a binder, rather than just dye in water.

Have you tried the forum on the Target web site? It is a really good way for their head guy, Jeff Weiss, to answer individual questions in a manner that allows everyone to benefit (and theoretically cuts down on the same question being answered twice). Plus, of course, you get shared information from other posters that is helpful.

As for toner coats, Transtint can be used to tint the Target lacquers (a little of the Target reducer mixed with the dye helps prevent gelling when it hits the lacquer). For heavier colors, they now carry Mixol pigments (which are pigments in the reducer solvent without any binder). Powdered pigment works, too (of course there's a fine line between translucent pigmented lacquer and paint...).



From the original questioner:
Wow, you can't beat WOODWEB for accelerating the learning curve! I called around today (as well as peeking in to the post every other hour), and I can see where the Transtints and H2O shellac won't work well together, whereas the alcohol cut shellac will.

Contributor J, you mentioned the 50/50 USL water seal coat. Have you found this an effective combination as a barrier coat with the Transtint dyes? I now realize that the Transtint dye in the Oxford clear stain base was probably the culprit in breaking down the H2O/shellac wash coat and contributing to the blotching and uneven resulting color. I'm now thinking of trying to drop out the medium brown Transtint from the clear stain base and using a burnt umber pigment instead. I've been advised that the Transtints are too reactive with the H2O shellac and re-dissolving the film as well as the shellac being, well, redissolvable in water. This would explain why the larger sprayed pieces had shifted color and blotched more than my 2'x2' sample board. More ragging off equals mixing of the dye coat with the stain coat and losing the preconditioning as well.

I have some sample boards in both dye-50/50 USL and 50/50 USL-dye. I'm now trying to lay hands on some Golden fluid acrylics burnt umber to use instead of the TT medium brown in the Oxford clear stain base. Dang school kids have cleaned all the art stores out of it around here! I've got 54 solid maple door and drawers to move onto, but I'm not pointing the gun near them until I can get the blotching resolved. If I can't source the Golden acrylics, I'll drop in the alcohol cut shellac and continue trying to work the same schedule.

I agree that the Target forum would be good to share the info with as well. I'm frankly scratching my head (or worse) wondering what the water based shellac is good for in a water based finishing schedule if it re-dissolves in water?! Thanks for everyone's advice. It's really helping a lot.



From contributor P:
Target has the Golden Fluids acrylic, but I believe they're going to stop carrying it. I actually just received a bottle from them, burnt umber even. Funny thing is I meant to order the burnt sienna.

From contributor W:
Target will be stocking the Mixol pigments to replace the Golden Fluid Acrylics. From what I've read on the Mixol products, you can add more pigment to your base and it will not gel. I think you can get Mixol at Woodcraft too...


From contributor A:
We use Degussa 888 universal colourant and it works exceptionally well. With our colour wheel, we can record our formulas and create a wide selection of opaque colours and pigmented stains. I found Mixol to be more of an artist thing, really, as the bottles are too small for tinting gallon after gallon after pail. When you have to add precise measures, a good tint dispenser from a paint store really makes a difference. Used ones run from $200-500 and hold 12 colours at 1-2 quarts of each.

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