Uneven finish

[Pat]

Hi

I tried KBS Rust seal (Satin black) for the first time today, with mixed results. I had some sandblasted car parts (disassembled wind screen wipers and some larger pieces), but because I'd handled them a bit, I decided to test the AquaKlean and RustBlast.

The first RustSeal coat went on nicely. All the brush marks smoothed right out, and I got a nice even finish. The parts were pretty fiddly to paint, so the jar I had transfered my stirred paint into was open for quite a while (maybe an hour). There wasnt too much left in the jar, so for the second coat, I used FRESH paint from my cling-wrap sealed tin (opened only while stirring & pouring).

I waited 3-4 hours before applying the second coat. To avoid spilling paint, I tried transferring the paint to a brand new jar using a clean 20mL disposable syringe.

The second coat did not work as well. The paint seemed not to stay evenly spread over the first coat. Even the paint on the walls of the jar (never before used) seemed to thin out to nothing in some spots, leaving small paint free circles behind. There were a few bubbles appearing while I was applying the paint too. This was essentially fresh paint. I have let this coat cure, but it doesnt have a nice surface like the first coat did. Its pretty streaky, as it didnt level out, and in parts doesnt completely cover the first coat.

I did first reuse the original brush, which I had given a quick clean with #1 thinner (it was dry and still soft). I thought this might have caused the problem, but I found a new brush, and got the same result. After starting I never handled the parts without gloves so I dont believe it was surface contamination.

Had it gone as planned, I would have applied KBS fusion within 6 hours and later put another UV resistant top coat over it.

I've watched the videos, and followed the instructions carefully, but I have quite a bit of this paint now, so want to make absolutely sure I use it properly!

So to my Q's....

* Any idea what might have caused the problem?

* To get a smooth final finish (before priming, top coating etc.), should I sand (400 grit?) and apply another coat of RustSeal?

More generally...

* Can subsequent coats still be applied sucessfully over fully cured RustSeal? I felt a bit pressured to apply a full second coat even though I wasnt confident that is was going on properly.

* Providing its not too humid and the second coat is applied within a few hours, can you use the same paint you originally poured out? Even if the lid's been off for a while? I cling-wrapped the remainder when first done, but eventually decided to use fresh paint for the second coat.

* Should a new brush be used for the second coat, even if the first was cleaned with the KBS thinners?

Regards,

Pat

[KBS Jim]

Pat,

Hard to say for sure what happened here, but it sounds like the first coat may not have been cured long enough. To answer your questions:

At this point I would let that last coat you applied cure well (24 hrs) then sand smooth, blow off any dust, then apply another coat of RustSeal. Thin the last coat just slightly (5%) with the #1 in case it has started it's curing. This thinning will allow the RustSeal to cure slower and thus lay out better. Was it hot and/or humid when you applied the RustSeal last time?

Additional coats of RustSeal can be applied over fully cured RustSeal within say 2 weeks. Just make sure the surface is clean.

Please be certain the first coat is at least dry to the touch (no fingerprints or tackiness) before applying an additional coat. Applying too soon can cause the bubbles and lack of flow. I would not use the paint you first poured out for the second coat as it is on the road to curing and will not flow out properly (no brush marks).

We usually use cheap chip brushes and toss them after each coat, but you can reuse a brush you've cleaned in #1, just be sure the #1 has evaporated off before.

I hope this answers some of your questions, if not, please feel free to give us a call at 877.548.9323.

[Pat]

Thanks for the reply

It may have been a combination of insufficient cure time and increasing humidity. It wasn't hot that day, maybe 18 oC. It had probably started to cool down in the evening as I put the second coat on. The next morning (after I posted), it was very foggy in Melbourne, so maybe the humidity had already started to climb? I have since bought a cheap digital humidity / temperature meter to be able to keep an eye on conditions a bit better.

It's reassuring to know that, in future, if I dont get the second coat on in the ideal time , I can still apply it later over the fully cured first coat.

But another question...

Is there any solvent that can remove cured RustSeal? I tried dip coating a piece I couldnt get my brush into. It was a clip and the RustSeal has now cured inside a crevice that is hard to get at. I thought if I hung the piece up, the paint would flow out better than it actually did. It worked for the first coat! The piece that should insert into the clip is now reluctant to go back in!

Thanks very much for the advice on how to solve my problem, and also the general tips.