Enclosure painting. More questions about weather/humidity.

[slashandburn]

I've discovered the wonders of decal paper, and as a result I'm painting more. Trouble is, I live in sunny Scotland and the weather is somewhat changable to put it mildly. Anyway, I think I've finally sussed out why some of my clear coats on my etched enclosures seem to dry (maybe cure would be a better word?) better than others. One case point that caught my eye was an 1590A etch, that was clearcoated MONTHS ago that I carelessly sat face down on top of a strand of 26awg wire the other day, and later found the wire had left an imprint in the lacquer. I was blaming the cheap brand of clearcoat I'd used, then the fact I didn't bake it. Then host of other explanations for it not "hardening" sufficiently over that lengthy period crossed my mind.

Meanwhile, last week or so I've been painting some solid colours over etch primer and I was noticing (might be all in my head) slight differences to the paint texture, and the only variable I can think of is the weather - I'm using the same paint, same prep, same drying process - sometimes the paint goes on fine and after the mist coats my main coats give me nice, smooth, pleasing glossy finishes. Other times I get different degrees of that "orange peel" effect I've seen many of you make reference too. I've also noticed drying times to be fairly widely variable from day to day.

tl;dr......Basically I think I've belatedly discovered the importance of spraying in the right temperature and humidity and I'm looking to draw on some of your experiences while I sit around pondering the longer-term implications of choosing a day where humidity was up past 80% to  get some painting done.

You so, when you get time folks - if you'd be so kind - what conditions do you aim for when your painting on the fly, and what problems present themselves if you have to paint in conditions that aren't ideal?
From what little research I've done, I understand 40-50% humidity is about perfect, with maybe 30% being the lower threshold and 70% being the upper limit of acceptance air moisture levels.

[EBK]

I feel your pain.  It's too humid here much of the time to clear coat successfully.  I've also experienced the hazard of allowing recently clear coated surfaces to touch a lacquered table.  It simply isn't fun to paint.  Better facilities (a real paint booth) may help, and baking the paint would probably be good too, but the clear coat I've used is quite volatile, so I'm a bit afraid to try the latter.

By the way, I've had somewhat better luck when I've taken the time to gradually layer up very thin dust coats of the clear stuff.

[slashandburn]

Cheers Eric. I'm not too frustrated watching this paint dry to be honest. They look okay and if they're failures I won't feel like I've wasted boxes (the enclosures were all failed etches, so they were already "wasted" in a sense. This is mostly just experimenting for future recovery missions.

Edited.   By god, I rant some.

Tl,dr:  yeah just pondering the extent of the problems from painting in non ideal temperatures and/or humidity. And possible solutions for making those non ideal days more workable. Bearing in mind a dedicated paint booth with its own dehumidifier is like not a feasible option. A dedicated toaster oven more feasible but I'm not sure it's the right solution.

[Kipper4]

During the rainy season and cold weather I use a block of wood to rest the enclosure on.
Clear coat in very light coats. I usually find 3-4 coats enough.
I paint in the shed down the garden
Transport the board and place it under a wall mounted radiator to dry.
Repeat until finished.
Leave to dry for a suitable period.
Meantime I do the box prep items.
Indicator led heatshrinking.
Pcb backing. Mostly hot melted card.
Sort out the washers and nuts for pots and switchs.
Solder the jumpers on a 3pdt.
Hotmelt offboard wires as a strain relief.
Solder jellybeans into sockets.
Solder wires to input and output jacks.
Strip and prepare wires for boxing.
By this time it's bedtime.
Inspection before boxing up as any further treatments may need doing now.
I find it satisfying and therapeutic.

Your weather may vary.
Ours is mostly cold northerly windy rain from the North Sea.
I presume coming from Scotland........

[slashandburn]

Cheers Rich.  Yeah I have a similar system and likely similarly shitty weather to contend with. Perhaps I'm overthinking it. I don't leave it under a heat source to dry and I likely go on heavier with the clear, but that seem the only difference.

Also the soft finish on that 1590A I mentioned was basically a one off, thankfully. I could have just been something like mixing brands or unknowingly spilling something on or near it, rather than my hairbrained new theory that I maybe applied then clear coat on a particularly humid day.

[EBK]

Also, some of the clear cloats won't go on well unless you shake the can for a few solid minutes.

[Kipper4]

I've had a cracklure surface before from mixing brands.
My local hardware store sells spray paint and clearcoat from the same brand.
It ain't cheap. I can't live with not doing it. Clearcoat is just the cherry on the cake.
Heck if it rains on one of my pedals clearcoat might help just prevent some outside damage.
If it gets wet inside. Might be a bit different.
I've yet to discover a waterproof pedal.
A pint of beer might look cool on the top of a cab but we don't do we.

[Ben Lyman]

After all this time, I finally got some helpful advice from a local luthier. The system seems to work for clear coating enclosures too.
I don't know if this seems so completely elementary to you guys as to make me appear like a dunce but I'll share it anyway.

1) spray a very light "overspray"
2) count 30 alligators
3) make a more substantial pass with the spray
4) count 120 alligators
5) repeat steps 3 and 4 as many times as desired, I go 2 or 3 more passes.
6) allow to cure at least 24 hours

Anybody else do it like this?

edit: OH! Almost forgot, I fill a small bucket with warm water and set the spray can in it for about 10 minutes before starting

[Kipper4]

It rains cats and dogs here not alligators.

What's that do?
Put the can in warm water.

[slashandburn]

Sorry to appear like I'm slapping your wrists for wandering off topic, I appreciate all your feedback and explanations of your process, but can we talk about weather conditions? Unless of course your all trying to tell me I shouldn't worry about those unless I paint outside?

I do the can in warm water thing too sometimes, since they get stored below room temp. I'd guess it mixes better when you shake it. I can certainly hear it "rattle" after less shaking than when I don't warm them up.

[Ben Lyman]

Ya, Iain got it, warms up, thins out, shakes easier, lays on more evenly, etc.
Sorry to drift off topic, I was also told to never try to spray if it's under 60º F outside.
I'm not sure about humidity but if you have a dry shed to do it in, maybe you could get a dehumidifier.
My "ghetto method" is to simply wait for a day that isn't rainy or foggy and then I know it's probably safe to paint.
Maybe that method only works in California... not quite the same climate as you got, eh

[EBK]

To go back to your weather/humidity concerns, I'd say always read the directions on the can.  My clear coat says:

Ideal Conditions:
Well ventilated area
50° to 85° degrees
Low humidity, do not use in high humidity

To me (and perhaps many of you), "well ventilated" means outside (I have no garage, shed, or paint booth).  Don't know​ why they felt the need to write out "degrees" after using the symbol, or why they forgot to put an 'F' for Fahrenheit, but for my more scientifically-minded and/or non-US friends, that's 10°C to about 30°C.  As for what constitutes low/high humidity, you're on your own if you use this stuff (Krylon® Crystal Clear, by the way -- not sure if that is an multinational brand).

[deadastronaut]

i spray outside and whip it indoors quick too...

wind across the clearcoat can create 'blooming' (white pearlescent type patches in clearcoat)
which is a pain in the butt...

for big jobs like guitars i spray outside. but have to wait for a nice warm , calm day...
then whip indoors and hang from my shower curtain rail ( much to the delight of mrs astro )

i do have a toaster oven too which i have used in winter outside..(i have a little coal bunker
outside my front door) and this is pretty handy...but NEVER use indoors.

5 to 10 mins in the oven and its cured enough to touch...and goes very hard too.
if you overbake it can give the clear a slight tint to it...

you can get these toaster ovens for 10 - 20 quid...might be your best option in scotland.
i got mine on ebay for 15 quid...
but now you can get them brand new for 20..

http://www.argos.co.uk/product/2445261?cmpid=GS001&_$ja=tsid:59157|cid:199888833|agid:17471076873|tid:pla-92279298513|crid:74692319553|nw:g|rnd:4420151952190853317|dvc:c|adp:1o1&gclid=CK638pKIg9QCFZQy0wodHZUI0Q

[karbomusic]

One case point that caught my eye was an 1590A etch, that was clearcoated MONTHS ago that I carelessly sat face down on top of a strand of 26awg wire the other day, and later found the wire had left an imprint in the lacquer.

Make your coats painfully thin and 1-2 minutes apart. Thin enough that it is nearly dry to the light touch between coats, as each new coat will reactivate and bond to the previous one. If too quick/thick (which is thinner than you think) the final top layer or two dry creating the equivalent of a paint can lid for the underlying layers which essentially never dry. This is how I learned that lesson, this is three days later and AFTER several times in the toaster oven....

[bluebunny]

I think Ben must live in a swamp.  All those alligators would give me the sh!ts.      I certainly wouldn't be painting outside...

[duck_arse]

we've only got crocodiles, but they come in two version, salt and freshwater. how many alligators to an hour, Ben?

[sorry Iain.]

[Kipper4]

Do they have grey paint down under?

[Ben Lyman]

Now now guys, lets stay on topic.
Duck, there are 3600 alligators in one hour. That means 2 minutes between coats (except for the 1st light overspray misting, 30 seconds)

That means the paint is actually still quite wet I guess. It goes against a lot of what I understand to be other peoples' "right" way.
I'm not saying I know anything about this at all, just saying I recently tried it and had very good results.
All 3 coats were done in 6 minutes and 30 seconds, then I popped it in the toaster for 10 minutes and walked away.
Enclosure was ready for assembly when I came back, I didn't polish or anything.

What I have been recently told (if I understand right) is that putting a coat on and letting it dry will cause a negative reaction when you apply the next coat, orange peeling, crackling, whatever, I dunno.
If you put the second coat on too soon, well... thats really no different than just pulling the trigger and standing there watching the paint flood everywhere.. so, that's no good either, right? Cloudy and/or drippy.

The happy medium is somewhere between 100 and 140 seconds... I guess... again, take this with a grain of salt.
I also do this outside on a toaster oven proof tray, on a clear day, then hustle it into the shed in between  coats, then into the toaster.

[slashandburn]

Ha. Cheers guys. It's pissing down here but no alligators thankfully. One of those ovens might do the job, Rob. It's only sorting out temperature, though.

To go back to your weather/humidity concerns, I'd say always read the directions on the can.  My clear coat says:

Ideal Conditions:
Well ventilated area
50° to 85° degrees
Low humidity, do not use in high humidity

To me (and perhaps many of you), "well ventilated" means outside (I have no garage, shed, or paint booth).  Don't know​ why they felt the need to write out "degrees" after using the symbol, or why they forgot to put an 'F' for Fahrenheit, but for my more scientifically-minded and/or non-US friends, that's 10°C to about 30°C.  As for what constitutes low/high humidity, you're on your own if you use this stuff (Krylon® Crystal Clear, by the way -- not sure if that is an multinational brand).

Eric, hitting the nail on the head. Sort of. You copped out on the bit about humidity that I'm bothered about.  As far as I gather, we warm up the can and bake to negate tempertaures that aren't ideal for sprying and drying respectively. I never see a lot of talk about trying to negate non-ideal humidity levels.

I'm wondering to what extent painting in high humidity has. In terms of air moisture (water) contaminating the paint and/or lacquer job.

I'm fully aware that I don't live in a swamp or a tropical rainforest where alligators and such might be a problem. The "problem" is that I've noticed some paint can instruction advising to avoid painting when humidity levels were below 30% or above 80%.  Our weather recently has had humidity well up past 80 which had me wondering, thats all. 

Sorry if im sounding grumpy. I appreciate all you all taking the time time to explain your processes.   A toaster oven might be a huge help in the winter and such but it doesn't help the overthinker in me keep wondering just how damp the air is.

[karbomusic]

It goes against a lot of what I understand to be other peoples' "right" way.

Just to be academically clear, my paraphrased right way advice came right off the can too, funny where the best advice hides. To the OP, read the can, compare to my post, I can't stress enough how much difference it makes to do it that way, probably why it's on the can.  Also, the overall process I mentioned is only good for about an hour, after that you have to wait 24 hours for subsequent coats - again though, that's the can of the paint I use(d) - go by what yours says on the paint can, but my main point was thin coat means way thinner than most of us realize, which means sort of dusted, not even covered, enough to appear dry to the touch before the next coat - that thin.

This even makes humidity less of an issue but again, the humidity/temp is also on the...