BPS paint time between coats?

[Ingersoll444]

When using BPS paint with hardner in it, how long do I have between coats? At what point do I have to scuff it up to add another coat? I am planing on priming some stuff tomarrow AM, and hoping to get a first top coat on them later in the day. Is that dooable?

[Steve (Magnolia, TX)]

When using BPS paint with hardner in it, how long do I have between coats? At what point do I have to scuff it up to add another coat? I am planing on priming some stuff tomarrow AM, and hoping to get a first top coat on them later in the day. Is that dooable?

You, you, you mean you're supposed to apply MORE than one coat of paint?

ROF ROF ROF

If I remember right 24 hours was the median time (humidity, temperature, etc. all have a bearing on paint drying times, but then, you knew that).

And yes, I'd scuff it up just before applying the next coat...

[mark777]

Paul,

I will try very hard to explain without over complicating...because it's much easier to do then to say.

The most critical part about flash, or recoat times is allowing the material to gas out. Which means allowing time for the solvents to evaporate and allow the material to chemically bond and adhere to the substrate (Primer) and then to each other. journeyman painters with as much, or more experience than I have will agree: Every painter goes through this period of adjustment of "Rushing flash times and re-coat too soon" and inevitably create solvent entrapment (solvent POP). Where the finished project looks great but hours later (sometimes days later) you have blisters, lifting and sinking that ruin all your hard work. Craze cracking, deep sand scratches and topcoat separation is 99% of the time from applying the next coat of color too soon.

Typically almost all manufacturers (PPG, Dupont, Sikkens, Valspar-BPS etc.) refer to 72° as the base line for primer and paint application...or the perfect temperature. In the real world, it is either colder or warmer so the reducers are either faster or slower...and the flash times are either longer (when cold) or shorter (when hot).

Regarding your primer and the allowable times for cure and top coat ready. Figure a minimum of 72 hours (3 days) at 72°. You can (and I do) shorten the time to 8 hours before scuffing with Scotch-Brite pads, but you must add 33% or 1/3rd hardener to your primer. Nowhere does it say that you can do this...including the back of BPS primer cans...but trust me, I have had long conversations with Valspar reps and chemists and they all agree that a maximum of 33% hardener accelerates the drying time without diminishing the products longevity or durability.

The simplest, easiest and fail safe method to prevent this AND runs, is to attach a piece of paper (painters paper, butcher paper or even newspaper) to a wall near your mixing table. Adjust the spray pattern and then make one full, wet pass with your gun and then proceed to your tractor parts and do the same. Every 5-10 minutes stick your finger in the paper sprayed area and check to see if the paint 1) is wet and runny, or 2) is sticky and stringy and 3) tacky like the sticky side of masking tape. If you go with #3 every time, I guarantee your paint work will be beautiful. You just have to remember to paint every coat (primer, color, clear or whatever) on your paper fist. And repeat those steps regardless of how many coats of material you apply.

Apologize for such a long winded post....

Mark

[mark777]

I forgot something...I would not try to re-coat if you've waited longer than an hour as you may have poor adhesion. Hardly noticeable unless you wash your tractor and large flakes come off....much like a sunburn thats peeling.

If you even suspect that you may have waited too long, it would be much better to stop, wait till the next day and scuff the entire areas, blow off, tack cloth and proceed with your next color coat.

Mark

[Mickey]

Nice lesson Mark. I'm not much of a painter myself but have always thought your #3 was the way to go. If you wait too long and paint is starting to get dry to the touch, you should then wait until full cure to recoat or you'll run into the problems you mention.

[Ingersoll444]

OK, so let me get this streight....


If I use hardner [and I am] it can be scuffed, and topcoated the next day?

[mark777]

OK, so let me get this streight....


If I use hardner [and I am] it can be scuffed, and topcoated the next day?

Yes. On the paint.
Yes. On the primer.

Providing you use hardener in both...
Would like to add that you have probably spent hours prep'ing your stuff. It only takes a few minutes to ruin your new finish, but you have to remember...that's ok. It is so easy to repair all of the flaws including solvent pop, fish-eye, a mosquito who drags itself miles across your hood, drops of sweat (happens allot) and the occasional dandelion snow flake that embeds itself usually at eye level and near the fuel cap.