Preventing Nubs in the Finish
Call them nibs or call them nubs, they're not good. Preventing them usually comes down to careful wiping and good hygeine. July 3, 2008
Question
As a cabinetmaker doing my own finishing, and getting better at it, I have one big problem that keeps irking me. It's all the nubs I have to sand down after the first sealer coat. Big, fat, heavy nubs! I have tried WW vinyl sealer as a wash coat after the stain dries so the first layer isn't very thick and the nubs would sand off faster. Or the first top coat as a sealer coat, Krystal, full strength. The WW has less nubs, but I feel adds an extra step. What am I doing wrong?
Forum Responses
(Finishing Forum)
From contributor F:
Take a hard look at the cleanliness of the area used for the finishing steps. If there's dust in the air or dust is kicked up from the floor, it's going to land on the product you are spraying, brushing, or wiping. Also, is the finishing product being strained before application? Are tools used for the application of finish cleaned well after each use? When I've had nib problems, I've traced the solution to correcting cleanliness problems about 90% of the time.
From contributor C:
Are you using an oil stain and then wiping with rags? If so, you're catching little pieces of the fiber from the cloth that are detached by the little raised grain that is doing the catching. Either wipe the stain off in the direction of the grain only, or spray stain the work, and you will see a dramatic decrease if this is the problem. Otherwise defer to contributor F's post.
P.S. Don't wipe the surface off with rags before you apply the stain or seal coat either - same thing will happen if you do. Use compressed air only and your hand.
From the original questioner:
If you don't wipe the stain off with rags, what do you use?
From contributor C:
Ah - you missed the part about going with the grain of the wood when wiping. You will know which way that is because if you feel any slight catching with a dry rag, that's against the grain; if not, that's with the grain.
From the original questioner:
Let's say I just spent 8 hours today staining and wiping with rags. What can I do tomorrow to help reduce what I may have done today? Tack rag before seal coat? Lint brush?
From contributor C:
You could try a piece of fine scotchbrite and then blow the surface off with high impingement air, about 120 psi and blow gun, or really fine sandpaper also. Do some samples if you can first to know what works best.
From contributor R:
If you don't have any luck using that there high impingemented air, switch over to cheesecloth for applying and removing the oil stain. Very little lint from that kind of cloth and it can be had real cheap at a fabric store. Careful if you use a tack rag on raw and/or stained wood... Too much pressure can leave the tack rag outline on the wood.
From contributor M:
When I was 19, I learned 120 psi, Tyvek suit, cotton apron, microfiber tack cloth. Your hand. You will be shocked at what a clean hand will pick up. I'm talking everything. Not only cleaning the surface, but zeroing in on leftover sanding grit. You'd never know it's there till you feel it. That is a major cause of nibs. Also, minimize air movement to only the booth. No fans or unfiltered outside air. Cleanliness is number one.
From contributor T:
All in all we try to keep our surface free of any kind of dust or nibs, but when staining something, I think the cheesecloth works the best because the fiber won't get hung up in the wood grain. The rags that you can rent are real bad since they have lots of lint left in them and the paper rags don't really absorb much material.
I have done finishing for many years and my father and grandfather were wood finishers also and all we ever used was the cotton cheesecloth. I still get mine from Mohawk finishing company and they come in a big roll so you just need to cut off what you need.
From contributor C:
I agree with the cheesecloth or even trace cloth for better staining results for sure. The material holds and disperses the stain/dye much better and gets into profile areas better also, but it can still occasionally be picked up to a very small extent. It's still good to use your hand for a final inspection of the surface before applying the coating. My father told me when I first got into this business, when I had asked him how long before I'd be a finisher, "Son, when you finally learn to see with your hands and feel with your eyes - then you'll be on your way to being a good finisher." I did not know right then what he meant, but I soon realized exactly what he meant. I wouldn't even think of spraying a finish on anything without first seeing the surface with my hand.
From contributor O:
That's an okay idea as long as your hands are clean and grease free. I've seen many a worker come back to the shop after a lunch that included fried chicken or a Big Mac or a chunk of leftover pizza. Lord knows what kind of goodies they have transplanted to the wood I'm about to finish. Let's remind everyone to wash up real good before seeing the surface with their hands.
From contributor J:
My guys figured out a little trick to get the oil off their hands after oiling their sanders. After they touch anything with oil, they find some sawdust (I know it seems hard to believe that we have any of that), and rub it on their hands so as to soak up any oil that is left on their skin.
From contributor C:
Although the sawdust might be helpful, you should still really thoroughly wash your hands before handling the goods. Some finishes are much more susceptible to trace contamination than others.
