Hello, I have a job to paint art (which I’ve done for many years) on a client’s furniture. But in this case they are small doors. This is a 2 year old house. The doors are totally unfinished pine with knots. I was afraid the knots would be a problem so I primed with Pro Coat. The resin came through. Four coats later, those spots are raised and sticky. I have now removed the Pro Coat over the knots with alcohol and sanded the edges to get rid of the indention where there is not primer. Now what? One person suggested white shellac. Three pro painters have told me to give up – it’s too green. I need this job – any suggestions how to seal these knots? Thanks-
Edited 7/15/2006 11:16 pm ET by Brazito
Replies
BIN 123 from Zinsser is a pigmented shellac primer. Use it and those knots will go away. BTW, the painter pros we work with always prime wood with BIN. I highly recomend using it...just remember to pick up some alcohol to clean your brushes.
Thanks so much for the information! I have always done my work on seasoned wood, usually finished, and this is a first for me. I'll get it today. Do you usually find it in a paint store or a chain home improvement place? Thanks again-
Paint store, hardware store, home improvement store.Frosty
The wood at this point is not green, presuming it has been indoors for a couple of years. If the knots are weeping so much resin that they are sticky there is no primer that will work reliably. Pure shellac or Bins, which is shellac mixed with a white pigment, will stop a certain amount of extractives and resin from bleeding through but they won't work reliably in the situation you are describing. If you would be out money if the resins bleed through your painting, I suggest you turn down the job because it will come back to haunt you.
John White, Shop Manager, Fine Woodworking Magazine
Thanks for weighing in - That is the same thing the painters I talked to said.
Because of the delay, while I have been struggling with this wood, the clients are aware there is a problem. I've been talking to them all along. I may just put it to them straight. If they want me to continue they should be aware these spots may bleed through. They can decide whether to proceed or not. I won't take responsibility. Of course the doors have four coats of primer on the rest, so if they want that removed I'll have to figure out how to handle that.
BUT, why are these knots so persistent? What is it?
Also, I'm thinking about oil and water.... Would a water base clear top coat be of any help to keep it down if they decide to proceed with the art? Thanks again.
Brazito,
Those knots are gonna give trouble from now on. Maybe you can incorporate them into the art...weeping eyes, or warty noses?
Regards,
Ray
Ha! :)
You can get it in spray cans. When we did our knotty pine den, the painter sprayed all the knots. Looked like a Dalmatian.Gretchen
You people are a gold mine. It affirms my belief that craftsmen operate in circles of excellence. The best hang out with the best. I appreciate this resource. Thanks.
Your thanks are appreciated but just remember--it may be worth exactly what you pay for it!! "o)Gretchen
"BUT, why are these knots so persistent? What is it?"
Gymnosperns are softwoods. One of the characteristics of gymnospermeae are resin canals. These are rare in angiospermeae (deciduous trees) although some deciduous hardwoods, such as the rubber tree, produce resin and the resin acts as a protectant against insect attack-- the resin gums up the mouth parts.
The resin in these pine knots has probably not been fixed via a kiln schedule that includes a period of high heat. This high heat treatment is incorporated into the programme for softwoods destined for furniture grade work and is usually omitted for softwoods destined for construction use. The former wood grade is intended to be seen whereas the latter is only a structural element and often hidden by bricks, plaster, et cetera.
The high heat treatment chrystalises the resin and fixes it so that it's solid and won't ooze out of exposed resin canals and things like knots-- the problem you're having. The high heat regime is not always 100% successful and there are failures, but the problem is largely taken care of.
Given enough time the resin in pine woods does eventually solidify on its own--- well sort of. The resin near the surface will often harden enough to hold back the liquid resin deeper in the wood. It can take several years and it's not always the case that this effect will occur. Cut surface resin free pine that's sealed itself naturally down the middle and the resin will start oozing again on the freshly exposed faces and edges.
That's probably a lot more information than you really wanted to know. In the circumstances in which you find yourself I'd guess (having not seen your job) the best you can do is try one of the shellac based sealers that others have suggested. If that doesn't work then it is likely the resin will keep oozing, perhaps for years. Your client will have to live with that, although as a last step and also a fairly expensive option, might be to replace all such panels that show these symptoms with pine kilned for furniture grade work. Slainte. Richard Jones Furniture
No, that is not more information than I wanted. That is exactly what I wanted to know. I always want to understand the process and science behind a situation. Its the same thing that makes me want to see the X-rays of my friend's joint replacement or know how my spouses diet works :)
Thank you
Brazito,
You got some good advice from the others. No need for me to repeat it. My message is a request for you to put up a few photos of your work. I do Bauernmalerei and Rosemaling and enjoy seeing the work of others who do various styles of painting on woodwork. If you have a few photos of your work, put up a post in the Gallery folder.
Thanks,
Mel
As a test on some scrap knotty pine I would soak the knots first with CA glue, then use epoxy to fill larger holes with epoxy. Then I'd use a primer.
Edited 7/17/2006 10:40 am ET by MrWilson
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