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-   -   Wood Trim - Spraying Latex on Oil (http://www.diychatroom.com/f4/wood-trim-spraying-latex-oil-118770/)

Twister 09-30-2011 12:05 PM

Wood Trim - Spraying Latex on Oil
 
Guys -

I'm spraying acrylic latex (Sherwin-Williams Pro Classic Acrylic Latex in a white semi-gloss) with an airless sprayer over an oil-based Sherwin-Wiliams eggshell that was sprayed on about 4 years ago.

I've asked around about how to do it and was told that in order to get the latex to adhere to the oil that I'd need to either scuff up the oil painted trim with sanding pads or use a product like Paso. I used the sanding pads.

Question: I was using 'fine' sanding pads because I didn't want to overscuff the trim, but after I vacuum off the sanded paint/powder, the wood trim feels exceptionally smooth. Are 'fine' sanding pads coarse enough to get the latex to adhere or should I try 'medium' grit sanding pads?

chrisn 09-30-2011 05:22 PM

You should be OK

Brushjockey 09-30-2011 05:28 PM

Smooth is good - what you want to see is "deglossed"- the shine taken off. That will give the new paint something to bite into (actually called "TOOTH")
If it was on a varnish coat ( and sometimes on an oil paint coat ) I like to use a conversion layer- a bonding primer.
Call it insurance.

Twister 09-30-2011 08:32 PM

Quote:

Originally Posted by Brushjockey (Post 739059)
Smooth is good - what you want to see is "deglossed"- the shine taken off. That will give the new paint something to bite into (actually called "TOOTH")
If it was on a varnish coat ( and sometimes on an oil paint coat ) I like to use a conversion layer- a bonding primer.
Call it insurance.

What's a bonding primer?

Brushjockey 09-30-2011 08:38 PM

Zinsser 123, BM fresh start, Glidden gripper,
Help me out here folks..
A primer whose main function is adhesion...

Gymschu 09-30-2011 08:45 PM

Quote:

Originally Posted by Brushjockey (Post 739199)
Zinsser 123, BM fresh start, Glidden gripper,
Help me out here folks..
A primer whose main function is adhesion...

Well-stated Brushjockey. Yeah, if I have the least bit of doubt about paint adhering, I use a BONDING primer. BJ mentioned the good ones, I like Zinsser 1-2-3, it's cheap and does what it's supposed to do........give the topcoat something to bite onto.

chrisn 10-01-2011 05:03 AM

Quote:

Originally Posted by Gymschu (Post 739207)
Well-stated Brushjockey. Yeah, if I have the least bit of doubt about paint adhering, I use a BONDING primer. BJ mentioned the good ones, I like Zinsser 1-2-3, it's cheap and does what it's supposed to do........give the topcoat something to bite onto.

I would also agree with the primer, if I was doing it, but I wouldn't be spaying.

kkeith 10-04-2011 09:52 AM

I never trust that scuffing is enough to provide a grip-able surface when applying water based paint over an existing oil based paint. Especially if the existing oil based is only 4 years old. I would only use an oil based primer or enamel undercoat brushed on as a conversion coating. I have found the water based bonding primers to not always hold adequately. Having to guarantee my work as a contractor, I can't take that chance.
I don't know if you are a DIY or pro, but if you don't have much experience spraying, you could make a real mess with overspray and buildups and runs. If you are good at spraying, you can't beat the finish of sprayed enamel. I suggest using an Fine Finish Tip which is different from a regular spray tip.

jsheridan 10-04-2011 10:07 AM

Quote:

Originally Posted by kkeith (Post 741934)
I never trust that scuffing is enough to provide a grip-able surface when applying water based paint over an existing oil based paint. Especially if the existing oil based is only 4 years old. I would only use an oil based primer or enamel undercoat brushed on as a conversion coating. I have found the water based bonding primers to not always hold adequately. Having to guarantee my work as a contractor, I can't take that chance.
I don't know if you are a DIY or pro, but if you don't have much experience spraying, you could make a real mess with overspray and buildups and runs. If you are good at spraying, you can't beat the finish of sprayed enamel. I suggest using an Fine Finish Tip which is different from a regular spray tip.

Hey Kevin, welcome to the forum. You'll like it here. There are a lot of HO regulars here who seem to have a good handle on things and are here to seriously learn new things. Makes it all worthwhile. Good first post.
Joe

kt82 12-11-2011 02:29 PM

"re:"I suggest using an Fine Finish Tip which is different from a regular spray tip."
when using the FF tip with Pro Classic Latex do you find you have to thin the paint
I am painting 1980 laquered oak kitchen cabinets . I have sanded (scuffed) and now want to prime
would I get better adhesion with the S-W oil base primer or a water based bonding primer like 1-2-3?

Twister 12-11-2011 03:18 PM

Quote:

Originally Posted by kt82 (Post 791328)
"re:"I suggest using an Fine Finish Tip which is different from a regular spray tip."
when using the FF tip with Pro Classic Latex do you find you have to thin the paint
I am painting 1980 laquered oak kitchen cabinets . I have sanded (scuffed) and now want to prime
would I get better adhesion with the S-W oil base primer or a water based bonding primer like 1-2-3?

For what it's worth, I'm not a professional painter but in the spraying I've done (using a 212 FFT [fine finish tip] and Sherwin-Williams Pro-Classic) I found I did NOT have to thin down the Pro-Classic. The paint bucket said that the tip size was .15 - .17 but the .212 FFT worked like a champ. I've got ceiling crown that looks as smooth as glass.

Good luck!


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