Minimizing Grain Raise with Waterborne Finishes
Finishers discuss pro methods to avoid or counteract the grain-raising effect of water in finish formulas. September 25, 2014
Question
I have made the switch from solvent based stains to water based stains. I have used GF enduro topcotes for a while without any stain under with great results. Now I am using the GF waterbased stain and dealing with the grain raising issues. I spray/wipe on stain, then spray GF sanding sealer, then hand sand with a foam pad to knock it down and then top with GF enduro poly. I sometimes sand through the stain even being careful, only on edges/corners. Is it easier to wet the surface prior to staining then re-sand and finish? I do some large work, bookcases, islands, table tops, cabinets. I would like to know how others are doing this and what methods works best for you.
Forum Responses
(Finishing Forum)
From contributor N:
I use a bit of the Target WB stain and it's not too bad on closed grain woods but on open grain woods - big time grain raise. So for those woods I spray water on everything first and then sand with 180/220 depending how high things have lifted. Even after this step you can still expect a little more raise after staining but it's not too bad. It's more work (two more steps) so I charge those customers who spec WB stain more.
From Contributor E:
We use only waterbased finished and use GF, ICA and Target. The trick with your GF is not to use the sanding sealer. Sand the work as fine as 220 to 320 prior to staining. Make sure you have no sharp corners. I use Mirka 240 grit foam backed pads to knock off fine edges and corners so the stain and finish have something to adhere to. Once your stain is dry put a light coat of the Gf topcoat. If you need to, once this is dry you can use a 500 grit Mirka foam backed pad on the flats only. Don’t try to sand the roughness out of the corners. Give it another topcoat then use a light touch with the 500 on the corners or even a grey or maroon Scotch-Brite. If you do sand through, get a bit of your stain and make a tight ball with a cotton rag and lightly touch up the sanded lines. Two more topcats sanding lightly between and it’s a professional finish.
We spray 15-20 gallons a month of this stuff and I have never used the sanding sealer except for the ICA because it is much tougher sooner than the others. Target EM2000 is very nice but it takes a longer time to get its initial strength. Waterbase is very different than solvent in the first hour after application in that it is dry but still soft. After five days all of the products have hardened up very nicely and are sufficiently durable. The ICA 2 component and the GF conversion varnish are really tough to beat - very nice products. EM2000 is still my favorite on cherry and oak. They all look very lifeless on maple without a toner r stain as they do not wet like solvent.
From contributor M:
More recent formulations of targets EM1000 really seem to pop/amplify the grain a lot more. I was laying down a coat about a year ago, and the effect was surprised me as being very solvent like. Something I had not experienced when using this product in the past. Another tip is that a just a few drops of honey amber trans tint per eight ounces or so of waterborne clear - it can really transform the look. This works especially well if you have other subtle layers of color beneath such as shellac.
From contributor B:
I think pre-wetting/sanding is a waste of time. I've used GF finish/stains/dyes for years. Our in house stuff is sanded to 150 and outsourced doors probably come in at 180. I think 220 or more is over kill and you can get issues with stain absorption and finish adhesion. I ease all edges/corners with 120 or 150 depending on wood species. Stain with either GF RTM stain or straight GF dye or a combo of the two. GF-SS then a scuff sand with 400 always staying away from any edges. Then synthetic/Scotch-Brite steel wool (purple) you gently wrap any edge for good adhesion and no sand-throughs. After a second coat of SS that's where I'll do a more aggressive sanding with 400 (by hand. blocks, pads, etc. are a sure way to sand-throughs - especially with today’s plywood veneers). Then a third coat of SS and another good sand with 400 and synthetic steel wool and TC with crosslinked pre-cat urethane for very plush finish. For a low traffic area a three step process will give you a nice tight finish. I also pre-tint all my SS and TC material with half a tbsp per Gl with GF orange dye for a warm solvent look. Over clear maple it looks like real close to nitro lac.
From the original questioner
Me too - I like the sanding sealer and it is less expensive. Thanks for the replies folks! My first full waterbased stain and finish job turned out awesome! Better than my oil stain and lacquers and it looks amazing. Now to just speed up the process and make things easier!
From Contributor O:
Unless needed for adhesion, I don't sand between coats. I put down the stain, let it dry sufficiently and then shoot on a thinned coat of finish. Overall I put on four coats and only sand after the third coat. I like to let the third sit for at least 24 hours before sanding, but can't always do that. By the time the third coat is on there's very little visible raised grain, and what little there is actually helps the adhesion of prior coats. I use Mirka or Abralon pads for the sanding.
From Contributor E:
In not using the sanding sealer, I am then eliminating having to have two guns or to switch over to the topcoat. The sanding sealer does its job but I personally feel it has a bit of weakness to protect the stain. I am not saying it is a bad product, it’s just my personal work flow. I should have clarified that in my first post.
From contributor M:
Sanding to 180 is fine with most waterborne finishes. Sometimes I have gone to 180 (solid wood) and then 220 (Veneers) to get dyes to match closer. I generally never exceed 220 grit. Any more and you’re wasting your time. For sanding in-between coats, I use either 600 or 800 grit, 3M 216U which was developed for water based auto paints. It’s expensive but doesn't load up. I can scuff an entire kitchen a couple of sheets.
From Contributor E:
To all who posted, what equipment are you spraying with? I use a kremlin MVX gun on a 10:14 pump which creates a lot of shear and micro bubbles in the GF finishes. I have to watch temperature, viscosity and air flow a lot.
From the original questioner
I use an HVLP gravity with 1.5 nozzle on my compressor. I have struggled with lacquers for years but after shooting the GF waterbased stains, clear poly, and enduro var I have no problems at all - best looking finishes I have ever done! I do need to watch temp and need to strain well (rust in the water pipes). It seems like colder temps make it worse and more air flow in the shop make it better.
From contributor N:
When it comes to WB I've quit the pump for the same reasons you cite (I have 10:1 too) and have switched over to using the pot and gun for WB 100% with no regrets and no more bubbles. I have a one man finish shop so I have to be prepared equipment wise for whatever comes in the shop (not to mention being a spray gun fiend), so I have a few set-ups.
My WB set-ups include:
Sata 1000K RP 1.3 mated to a two gallon stainless pot – it’s the finest spray gun I've ever wrapped my hands around. This thing produces an absolutely flawless WB finish but uses 15cfm.
Devilbiss GTi HVLP 1.1/1.3/1.6/1.8 with a 2000 air cap mated to a two quart pot - another fantastic spray gun. Perfect finish and super low over-spray but uses 16cfm.
Devilbiss CVi RP WB gravity gun 510 air-cap 1.3/1.4 and once again this thing lays down a perfect finish, uses only 10cfm and is pretty darn fast. For stains and toning/shading I have a CAT SLP .8/1.3 with the RP air-cap mated to a two quart pot another great set-up!
From contributor J:
I use general finishes only for all of my new builds. I use the top coats over the stain for the reasons mentioned above. I typically do not pre wet the wood before final sanding to 180. I have never found that I can make good time with the grits mentioned above. I wouldn’t have any arms and hands left if I did my scuff sanding with 600. However I am in the throws of a white oak kitchen and am having a lot of open pore swelling on the solid wood (veneers are ok). In the past I have found that a wash coat will help with this, but got away from doing wash coats over the last couple of years because they are time consuming and not always reliable. I do wonder if in this situation a pre wetting before sanding to 180 would have helped this swelling. Red oak is a whole different beast and usually needs a wash of dewaxed shellac before proceeding with WB.
I regards to equipment I have an Asturo eco ssp with a two gallon pressure pot (1.3mm tip set for clears), an asturo eco sx, and a titan 440i airless (308-411 tip for clears). I can get some bubbling with the airless, but if I lay a wet enough coat they will flow out.
From Gene Wengert, forum technical advisor:
You will have more grain raising with dull sandpaper. With dull paper, the grit on the paper tends to push the fibers over rather than cut them off cleanly. Also, excessive pressure pushes rather than cuts. You can also get grain raising with loaded sandpaper. Change sandpaper more often is a good rule. After sanding, if the surface seems heated, be careful. Softer, lower density wood will have more grain raising, especially if the wood is over 7.0% MC. The drier the wood, the stiffer the fiber and the less need for sanding sealer to stiffen the fiber. Note that even a dense wood like oak will have a weak fiber (called tension wood which is common in crooked trees, around knots, and in a leaning tree).
