I need to do some touch-up brush painting of nuts and bolt heads on the running gear of my dad's 1900 Waverley Electric.
It was spray painted with PPG Omni MTK Urethane 2K (Chevrolet Candy Apple Red).
For application with a brush, the painter who did the spray painting said we should mix it the same as when it was sprayed - four parts MTK Urethane basecoat, one part reducer and one part hardener.
The urethane basecoat in and of itself is already very thin and watery right out of the can even before the reducer and hardener is added. We mixed a very small batch via the instructions above but it is not thick and sticky enough to apply with a brush. We have been letting the mixture sit and it has thickened up a little bit but not enough to brush.
Should I have just left out the reducer or should I let the mixture sit until it becomes thick enough to apply with a brush?
Should we use a different basecoat for brush work, such as enamel instead of urethane?
Thank you for your suggestions.
Erik, just leave out the reducer (or reduce only as much as is desired to get flow). Reducer affects flow and flash time, but those instructions are written for people that are spraying. Continue to use the specified amount of hardener because that is essential to how it sets up.
Letting what you have sit won't help the situation any because once it starts to get thicker, the mix is already starting to kick -- harden rather than thicken.
What are you using for a brush? For bolts I find that a pinstriping brush works well. You can load it up better than an artists brush and some artists brushes tend to be stiff, thereby cutting down to the surface rather than allowing the paint to flow on. It's a game finding the brush that works right for each situation.
(Message edited by WMH on August 06, 2016)
Just mix the base and the hardener. If you need to reduce it, use a little MEK. If not just use it as is.
Erik, I don't have a ton of experience here, but based on my experiences, probably adding hardener only would have been ok. But, the other issue you have is a Candy style paint. These are inherently thin and transparent by nature because they need a basecoat of some sort---typically silver, gold, black or white.
For touchups---again, I am no expert, I really like single stage enamel straight out of the can. But some colors can't be mixed single stage or enamel from what I was told at the paint supply house.
Thank you Walter and Royce - makes sense.
I'm using natural bristle artist brushes.
I have zero experience with two part paint/compressor spraying. The other antique cars in the garage were painted 55-65 years ago with Dupont Dulux so touch up with a brush is straight out of the can is never a big deal.
I have found that when I try to touch up with just the basecoat the finish is somewhat dull.
So I mix 1 part basecoat and 1 part clearcoat and the clearcoat hardner as per its instruction sheet and get paint that matches the gloss of finish on the item.
My basecoat doesn't call for a hardener though.
You might consider a air brush from HarborFreight. It works good for spot touchup and doesn't require special skills like a regular spray would.
Mare sure the heads of the nuts and bolts are plain metal, not zinc or anything, and then prime before painting.
For modern bolts, grind or file off the markings, then to remove the zinc coating rinse them in muriatic acid, then neutralize with some baking soda and water, dry, then prime.
: ^ )
When I did touch up with the Omni, I used a medical disposable syringe to measure out the parts into a plastic cup and used that to paint from. It will leave a raised edge but that can be sanded/buffed.