ProWallGuy said:Sorry if I was misunderstood, but I'm no 'hit & run' type of guy. That figure alone was for applying 1 coat of paint. It didn't account for prep at all, including removing the door (if applicable), sanding, scraping, stripping, caulking, filling, etc. If there is evidence of a problem, (ie failure due to latex over oil), then the price obviously goes way up. The price quoted above was just a plug-in price for 1 coat of paint. I figured I charge $55 per man hour, and it only takes approx. 1/2 hour to paint any kind of door. So at the end of the estimating process with materials, overhead, profit, and whatever prep is required, you are probably right with the $100 figure.
So once again, sorry if I was misunderstood, I typed that on the fly.
And I rarely spray anything, its all done by hand.
Whats the failure that happens when you use a quality latex over oil?? I can see a failure with oil over latex more likely.
ProWallGuy said:Oil over latex adheres with no problem. Never seen a failure there. Latex over oil, whether quality or not, doesn't adhere very well at all. Seen many failures where latex was applied over oil without the appropriate (alkyd) primer and/or prep.
S.W.C said:It's been my experience that oil over latex works just fine without any special prep.
As long as base is acrylic, the oil should go on it good.
Oil has a more dense molecular structure than acrylic, which makes it's more difficult for the acrylic to stick to it. It's like trying to paint silicone.
Oil, on the other hand, will penatrate the porous structure of the acrylic. :Thumbs:
Unregistered said:Interesting...what do you mean by ..more dense?...I think the problem with oil over latex is that oil is more brittle and won't flex like latex so it is more likely to crack...especially in exterior settings...and once a coating cracks there is a entry way for moisture and a coatings failure is somewhere around the corner....maybe in an interior setting is 6 of one and a half dozen of the other....but I still don't really buy it..the bonding of oil to a surface depends much more on penetration..where as the adhesion of latex come from curing into a coating that is pretty much one continuous film...at least this is what I've come to believe is true...and it seems pretty accurate.
Teetorbilt said:SWC and unregisitered, most folks are not particularily concerned about HOW it works on a molecular level.
Maybe we should say that putting latex over oil based paints without suitable prep and primer is not a good idea.
I will not enter the oil over latex arena as I have never done it. I have always stripped the latex off and gone back with oil based enamels, scuffing as I went.
If you are truly concerned with adhesion on a molecular level, I can contact a few classmates that can give you the entire envelope.