[CApainter]

I've had PPG Pitt Tech Plus adhere pretty well to aged oil based exterior metal siding. No primer, or sanding, just pressure washed and sprayed on. I've also done the same with doors except I degreased and evenly scuffed the surface before applying the PPG Pitt Tech Plus. I got away with it because Pitt Tech doesn't peel like waterbornes of old.

With that said, I would not recommend painting over oil based coatings with a waterborne finish unless the surface was first properly freed from contaminants, scuffed, and primed with a bonding primer.

Remember, painting is very subjective. There are many different variables that help determine the level of best practices a painter is obligated to. For example:
1. The level of detrimental exposure the coating will be subjected to
2. Bare substrates verses previously painted substrates
3. Aesthetic expectations
4. Difficult areas to access
5. Inspection/documentation (QA/QC) requirements
6. Budgets
7. etc.

 

[CApainter]

Pitt Tech Plus 4212 HP (36% SBV) has a recommended DFT range of 1.5 mils - 4 mils.
The following would be the theoretical coverage if the project coating specifications required the maximum DFT per coat:

4 /36% SBV = 11.1 WFT

1604 / 4 x 36% = 144.36 sf per gal.

 

[CApainter]

These are the facts and calculations that a Certified WWTP contractor or water tank paint contractor would use to calculate the amount of materials. The 1604 rule a[[lies to all types of paints. E.G. the Old Exterior Super Paint was 40% solids by volume. applied @ 2 mils recommended wft. rounded off for example purposes. 1604 times 40% equals 641 sq feet. @ 2 mils wet would be 321 sq feet. I do understand the spec data sheet is now expressed in WFT of 4 or 5 mils, labels used to include spread rates and are now omitted for comparison purposes. Ask your paint supplier if he knows what the solids by volume are in his can of paint? The second variable is the quality of the titanium/ or filler, Type 1 2, 3 or 4? 1 & 3 are used in flats etc. I hope everybody uses more than one method to calculate a job?

I thought the 1604 rule applies to DFT not WFT. In other words, a gallon of a 100% solids material spread at a thickness of 1 mil WFT would cover 1604 sf and would dry at 1 mil at 1604 sf because there are no solvents to evaporate. Given the example you provided (40% SBV @ 2 mil WFT), I get the following:

2WFT x 40%SBV= 0.8DFT

1604 divided by 0.8DFT x 40%SBV = 802 sf per gal.

The problem I see is the 0.8 DFT per coat seems too thin.

 

[CApainter]

True, An 100% epoxy goes on at the same millage wet or dry. I responded without proof reading. Any input on the manufacturers no longer expressing the solids by volume? Remember Spead. Ultra by Glidden in the 1990"s? Self cleaning, meaning the titanium one was prone to chalking and resistant to mildew? Remember when zinc was the finest biocide and mildi cide?

Maybe the manufacturers are no longer interested in following sound technical information protocols for their products because most of the end users are either ignorant of coating dynamics, or could careless because subjectivity rules the day in an industry driven by illusion and one's own perception.

 

[CApainter]

Excluding solvents, I doubt there is a can of latex paint that costs over $10 a gallon to manufacturer. Titanium is almost an unknown pigment in todays paints. 2 & 3 coats are the new norm. It doesn't have to be that way. Big paint contractors and paint companies come and gone from what I have seen since 1966. The only lasting theme is quality workmanship using quality products. My contractors complain that they are getting the same prices that they did in 1999, only the cost of paint has more than doubled. Find a special niche, build a happy and satisfied customer base, have a trade that cannot be duplicated. There is lots of competition out there, be the best you can be.

My niche was being the reliable Mule a customer could pack as many of their requests on as possible. Of course, I was very popular and often spoken well of for my endurance and low maintenance.