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Kol__

Painting techniques and time between coats

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Hi guys,

This weekend I should hopefully be attempting to paint my first body shell - hard body Grasshopper II (although I have a few shells here so might spray up more than one). I've kept an old cardboard box to use as a spray booth in the shed. I picked up 4 grades of the Tamiya pad sanding sheets stuff, Tamiya fine surface primer and some normal Tamiya primer (what is the difference there?), Tamiya TS paints and a Tamiya clear coat. I read that the primer is not needed for the TS paints, but surely it will add another level of adhesion and durability to the finish?

Any tips? How many coats at each stage of the paint job - primer, top coat and clear coat (after stickers)? And what is the drying time between coats of the different types of paint? Primer, top coat and clear coat - how quickly can I give them a gentle key over between coats?

Temperature wise, it's getting a little colder here in the UK. I plan to put the heater on in the shed and get it to say a comfortable 18 degree C and pop the paint cans in a little warm water before spraying. Hopefully that will be ok, can't so anything about the levels of humidity, although I don't think it'll pose a major problem yet at this time if year.

Cheers for any input here:)

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I'm not an expert on hard bodies by any means, but Tamiya paints do like to be warm before spraying.  So, this is how I do it - bear in mind I don't go for concourse finishes, just something acceptably tidy that won't flake off first time it touches a piece of cardboard.

0) before you worry about paint, make sure you key the body, then wash it with fairy up liquid and thoroughly dry it with a clean, non-floof-dropping towel (I find teatowels or microfibre cloths best).  Not sure what your water is like in Farnbro but over here in West Wilts it's so hard you could hit someone over the head with it, if you leave a water blob on the surface it'll dry into a ring of healthy minerals and be visible all the way to the topcoat.

1) Try to get at least 20 degrees in the paint area before you paint.  As well as helping paint adhesion, this will drive away any moisture in the air.  Paint cools as it expands and this encourages moisture to condense on the freshly-painted surface.  TS paints are more affected by moisture in the atmosphere, which manifests as a fogging in the colour and there's not much you can do to get rid of it.  If you can get the heat directly in the paint box, great.  I use a pair of 500W halogen worklamps as they really blast heat into the area, despite being terribly inefficient as a light source they are fantastically efficient at getting heat into the paint area.  Even in midwinter, the temp gauge in the spray bench will get above 20 degrees after 10 minutes or so.  It would take all day to reach that temp on the bench with a 2000W oil-filled radiator positioned nearby.  Pretty sure halogens have been banned in the UK because people insist on bolting them to their garden walls and letting all that heat escape into the atmosphere while floodlighting their midnight barbecue at 3 polar bears per minute.  Be warned that a gas heater will emit moisture into the air.

2) Tamiya paints like to be warm before you get a good spray.  I use hot (tap) water.  I have put cans into water straight from a boiled kettle before and I haven't had one explode yet, but tap-hot is probably fine.  (Plus if you get the can too hot you can't hold it to spray).  I rest a tub of water on top of my halogen lamp and put the can into it, if the lamps are on for a while they'll get hot enough to keep my coffee on the boil all morning.  Halfords paints don't seem to like being warmed first.

3) Definitely use a primer.  I don't think I've ever painted a TS paint without a primer, but I doubt the results would be very good.

4) Number of coats - keep an eye on the finish between keying, basically.  Primer will probably want 2-3 light coats but if you're too aggressive on the keying then you'll go through on the corners and hard edges, and then your colour coats will look different where they've adhered direct to bare plastic.  Once you're onto the colour coat, stop painting once you've got the full colour showing strong.  If you're going for boxart then white paint on white primer on white body, you won't need many coats.  As for lacquer - how thick and shiny do you want it to look, and how heavy do you want the body to be?  The more you add the tougher the final job will be, but at the end of the day if you flip it on tarmac you're going to scratch it anyway, so I wouldn't go overboard.

5) Be careful with the clear coat.  Tamiya stuff is typically good but I've had some other brands where the lacquer has gathered in a blob under the nozzle during spraying, and then gets blown off once it reaches a certain critical mass and leaves blobs all over the shell.  If the colour coat isn't fully cured, the big blob of solvent will eat right through it and lift it off, ruining the whole job.  Been there, done that!  So, do the lacquer in short bursts, check the rim under the nozzle and wipe it off if anything is gathering there.

6) I often speed the drying time using a hair dryer, but be warned it will kick up overspray dust off the painting area and blow it all over your shell, and if it's a Workshop Hairdryer (which is much safer than borrowing the wife's one, trust me) it will be full of dust when you switch it on, so point it away from the body and give it a run-up to clear it out.  Also if you have your shell delicately balanced on some paint pot lids or takeaway tubs, it might blow it over and land your damp paint job in the overspray dust.  You can be really aggressive with the hairdryer heat without any adverse effect, plus it helps warm the surface to get the next coat on.  However, even with plenty of heat to speed up drying, the curing process is a chemical one and takes time.  I find it's OK to go 15 - 20 minutes between coats of the same type if you're using a hairdryer, that should get it hard enough to key for the next coat, but an hour between coats of different types is advised to avoid any paint reaction.  Pro painters might advise a day between colour coat and lacquer, although I've put Halfords clearcoat over Halfords colour coat after an hour and had no obvious problems.

When I'm doing polycarb bodies, I will literally hairdryer, spray, hairdryer, spray, hairdryer, spray, hairdryer, pull of masking, spray, hairdryer, spray, hairdryer, pull of masking, hairdryer, spray, hairdryer, spray, hairdryer, pull of window masks, pull of protective film, add stickers.  I've done 3 colour bodies + backing coat in under an hour.  But that is with PS paints which I find are more forgiving and cure quickly under heat.

7) I'd probably leave lacquer to cure in the house overnight before adding stickers.  If you make a mistake and try to pull the sticker off to reseat it, it can pull the lacquer off with it, and if you leave any sticky residue behind, the sticky stuff remover will eat the uncured lacquer right down to the primer (done that too).  You can, if you like, put the stickers onto the colour coat, and then lacquer over the top.

The GH2 is a lean, skinny body and should be forgiving for all but the worst paint mistakes, treat it as a learning experience and have fun, absolute worst case scenario is you have to spend a day with the paint remover going back to bare plastic to start again and you've wasted £20 or so on paint.

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I build tons of static models and used quite a few cans of TS (and AS) and also live in the UK and had sprayed in the shed right through winter, even when it snows. 

Tips:

1. Wash your model, use your bath with Poundland dishwashing liquid and hot water from your tap (not boiling!). 

2. Allow to dry COMPLETELY. 

3. Keep your model indoors warm until just before taking out to spray. 

4. As stated, preheat your spray cans, soak in hot tap water. Shake, before soaking, shake after soaking. 

5. Immediately take in after spraying to dry Overnight (8 - 12 hours) indoors while protecting from rain or snow if the path from out to in is exposed. Do not let it dry in the shed! 

Now for the details. 

1. Prime, I used to use Tamiya spray but now uses Mr Surfacer. This is even more important as RC cars are treated more harshly than static models. I used to use Tamiya spray primers but now due to logistics and cost, uses Mr Surfacer. 

2. Sand between coats, I don't do that but good model maker does. This brings out the shine. I also don't see the point in doing so for a RC which will get scratched anyway. 

3. Light coats, while heavy coats may seem to be more shiny, sand and light coat is better. 

4. 2 coats of primer, 3 coats of paint, 2 - 3 coats of clear, with sanding in between. 

5. Humidity is (for me) not a huge issue as I keep the model indoors until spraying and take it in straight away. It is a huge issue for pure waterbased paint, which TS are not. 

6. Far as I had experienced, there is not a great due of difference between surface primer and fine surface primer, just color, IIRC. 

Some final words. 

1. Airbrush if you can. I used to love spray cans until I figured out how to use the airbrush(es). 

2. If you are painting a runner body, you will probably discover it is not worth the time as it will get chipped, scratched, etc... Best to get a spare body for display and one for running. (note, this is my personal opinion after seeing how a painted Lunchbox turned out) 

3. CC for CC, Halfords paint is cheaper than Tamiya, and work just as well. I will still use their spray if not for the fact that the nearest Halfords is 200+ miles away from me and I airbrush now. 

PS typed on my phone, tiny screen so apologies if my answer seemed disjointed and I missed something. 

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For me I mainly use flat TS paint so the dry time is significantly shorter than gloss paints.  I only wait 2 min between coats, do all the sanding #1500 as needed between coats and re-spray.  For gloss I give it a couple more minutes between coats, and finish with a wet coat for high gloss.  I do not use glossy clear coat.  

Cure time is about 2 hours for flat paint, gloss I usually let it sit 5-6 hours as I use a wet coat at the end.  I tend to push the dry times to the limits so take your time. 

I don't use primer unless the plastic color is significantly different from the paint I want to use.. like if going from red molding to white, or painting 2 completely different colored panels a same color, I would use primer.  

Not sure what color you are planning to paint, but if white, spray a bit from a distance as it needs to be in a powder-like form to properly layer on top of each other.  If one was to spray thick layers it will just melt the previous layer and end up not layering at all leaving an ugly blob of running-like paint.  

I always paint inside the house 65F-75F with humidity less than 50%.  High humidity can cloud paint so I'd watch out for that.

For clear coat search online about the cracking issues people had with TS and make your decision.  I only use acrylic clear when matting things down.  No cracks.

GL. 

 

 

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Only a few things to add. 

Tamiya recommends 60/60. [Above 60F (15.5C), below 60% humidity]  I think of it as absolute minimum.  Today is a perfect day to spray paint for me. It's 65F(18C) and 50% humidity.  A little warmer and a little dryer than the minimum.  

1) Beware of the color of primer.  If you want to use primer, use white primer.  If the primer is in gray and you happened to spray white or bright color on it, it will forever be dingy-white or dingy-yellow.  If the primer is pure white, no worries.  For Tamiya's white shells, I don't usually bother with primer, but if I were to paint white, I would use white primer because Tamiya's yellowy-white could be seen through.  

2) I spray horizontally. (obviously, for a hard shell, you'd paint on the outside, not inside like the picture.)  If you spray horizontally, the heaviest droplets would fall.  You will get finer, even mist.  I spray 3 light layers.

62dXN3P.jpg

3) When you are finished with one layer, you can clear the nozzle.  Flip the can upside down and spray in the air for half a second. (Once you clear the nozzle, you can spray a half-spent can a year later, if you want to.)  Between layers, I give half an hour.  On a hot and dry days, as little as 10 minutes.  If I paint after sundown and the humidity is up, 45 minutes to an hour.  

4) I wick away the droplet that forms at the nozzle every time I use it.  If you leave it, it can sputter as if you are trying to whistle with a mouthful of water in your mouth.  

  txEGPow.jpg

CCaNiPd.jpg

Good luck with your shell.  

 

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Thanks guys, really appreciate such detailed input, I certainly feel more prepared now, many thanks! I'll try not to be too precious with this one, just enjoy it and accept that it's my first one and will be soon be bashed anyway. As long as I get some experience to then be able to do a better job with future attempts then I'll be happy. I'll be sure to post up the results on here, cheers:)

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A word of warning if you choose to spray indoors; without proper extraction, you will eventually notice a layer of "dust" settling over your stuff. This "dust" are in fact very fine paint and cannot be easily removed. My guess is, based on your cardboard spray booth plan and your questions, you do not have regularly build or spray models. One or two is probably OK, but if you build a few dozens a year like I do, it will soon build up. 

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This is an excellent thread.  I was going to ask about a lot of this.  Thank you all. 

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As @Juggularpointed out, be careful of your primer. White is usually best if you do not know what you are doing as there is almost zero chance of messing that up. Do not even try black primer unless you know what you are doing. I once experimented with black primer and yellow finishing, trying to achieve Dunkelgelb and 10 coats of yellow later, it is still black! 

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When painting, less is more. Do many fine coats rather than few thick coats. It comes out nicer but it takes longer. 

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Hey guys, so sprayed up the Grasshopper 2 shell with primer and top coats of TC paint. It went pretty well and the cardboard spray booth worked quite well, but I'm glad I covered up my motorcycle with a couple of old sheets - thanks for the advice on the 'dust' @alvinlwh, I would've been gutted if this had got damaged...

knc3Zc6.jpeg

The primer went down well enough, seemed to leave quite a dusty finish between coats. Sanding with the 1500 pad after the first coat seemed to remove paint from the edges, even with light pressure. So I just went with wiping down the shell with a micro fibre cloth between coats.

Whipped up a quick stand, as I have 3 Mad bull shells to paint after this one, which are the same mould as the Grasshopper II shell. Used blue tack to keep the shell in place on the stand.

ESdJYEg.jpeg

Primered x4 coats, although one of those was really only to recoat the areas where the sand paper had removed the primer

Els18Gd.jpeg

Top coat x3. My boy loves blue, so hopefully this blue with the dark blue and red original stickers you can see on the worktop below the shell, will go well together.

0aVmBxp.jpeg

I'm quite happy with the finish, for my first attempt anyway (the last time I used a spray can was to spray a Honda exhaust manifold heat shield with heat proof paint about 10 years ago and before that I can't even remember). No bits of dust or any real blemishes in the paint, so it's been a good learning experience so far.

There is a slight texture to the paint, you can see it where the light is hitting the shell in the pic below. I wouldn't exactly say it was orange peel, but it seems like a very fine version of that. This is down to technique I assume? Any tips on how to avoid in future?

bJdRnle.jpeg

Plans next are to apply stickers and a clear coat... then it goes off to die a painful dead at the hands of my son:lol:

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@Kol__that's a cool  bike. Wish I still have one now, been 20 years since I owned a bike.

Re your texture/orange peel, hard-core static model makers will heavily coat the clear and sand it down to a mirror finish for a showroom shine. Personally I don't bother and will never do so for a runner. 

Re your stickers, if you intend to repaint further down the road, do not clear coat over them, they will be difficult to remove then and leave an outline that takes more sanding to remove in prep for painting. 

In the future, perhaps you can consider fluorescent paint, that will delight kids even more although Tamiya only got 2 TS in fluorescent, 36 Red and 96 orange. 

 

 

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@Kol__ Good job on the restoration.  

Orange peel can be good to hide surface imperfections so sometimes I intentionally induce it by spraying gloss color from a tad distance and light on the last coat.   And use polish (compound) to gain back high gloss.

If you want to not have orange peel I go wet coat at the very end where it is near running.  I usually do that for gloss finish.   No orange peel.   

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I have 2 nots that i learned the hard way (as i am best at falling)

1. Do not spray PS paint if its - outside (and you are spraying outside ofc), its like a clown in the rain.

2. Do not Do a Mika Blue spray job on black kitchen table thinking your wife/girl/man wont notice (even if you do have a neat cardboardbox setup going on), almoast lost all my rights to my hobby right there.

Lots off how to do it right here so i leave you with 2 nots

 

 

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On 10/30/2021 at 10:08 PM, Willy iine said:

@Kol__ Good job on the restoration.  

Orange peel can be good to hide surface imperfections so sometimes I intentionally induce it by spraying gloss color from a tad distance and light on the last coat.   And use polish (compound) to gain back high gloss.

If you want to not have orange peel I go wet coat at the very end where it is near running.  I usually do that for gloss finish.   No orange peel.   

Cheers @Willy iine, with regard to the wet coat, is that best achieved by a slower pass with the paint can? Or more overlapping of the paint passes? Or can closer to the body shell? I did have one point where I sprayed more primer on the roof of the shell and I think I know what you mean by wet coat - I thought that area might run, but it didn’t and I think it did dry with a slightly smoother finish.

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55 minutes ago, Kol__ said:

Cheers @Willy iine, with regard to the wet coat, is that best achieved by a slower pass with the paint can? Or more overlapping of the paint passes? Or can closer to the body shell? I did have one point where I sprayed more primer on the roof of the shell and I think I know what you mean by wet coat - I thought that area might run, but it didn’t and I think it did dry with a slightly smoother finish.

I don’t recommend spraying too close to the object as the blowing force from the can can potentially induce runs.  

For wet coat I apply in a slow-ish back and forth motion until the mist of paint all connect to each other into one big solid wet coat.  The trick is not to over apply as it can cause runs and not to under spray either. 

If you notice you over applied the paint, then gently keep rotating the object back and forth side to side against the run to allow the running paint to disperse and not get caught in one direction.   Usually one can save running paint.  

Hope this helps! 

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Honestly the best thing I learned (from the late great Rad22) was to use MicroMesh for rubbing down in between coats (not regular wet and dry - it cuts way too fast and unevenly for model use).

Quote

There is a slight texture to the paint, you can see it where the light is hitting the shell in the pic below. 

It's a non-issue but I would recommend not glossing straight over it and instead cut it back slightly with MicroMesh. You can get it in a selection of grades for a few quid on eBay. Start with maybe 4000 grit with soapy water and just knock back the surface slightly so that to the touch it's a little less bumpy (take the very tops of the bumps off basically - all you need is to flatten it very slightly). Then start clear coating, with a good 3 days in between coats and 4000 grit in between. After three clear coats start with 4000 grit and work your way up through all the grits until it has the shine you want. I usually stop around 8000/10000 or so because going further it starts to look like glass and amazing but unrealistic.

99.9% of a great finish is basically patience. It's really time consuming, especially on large or detailed models, but it's actually quite easy. And really rewarding.

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Thanks @casethejoint, appreciate the advice. I waited a couple of days to let the paint harden and then added the stickers (first time doing that and it was tricky here and there, but very enjoyable, obv really brings it to life!). Since then I've let the car sit as have been doing other stuff. I assume there is an ideal time to add clear coat i.e. perhaps a few days after so that the paint has hardened but not fully cured, so I may have missed that window. I now need to get back to it and clear coat it, so I was thinking I should key up the surface a bit. However, now I have the stickers on there I guess I'll need to be careful and avoid them. Unless the super fine 4000 grit could be gently used over the whole body, including the stickers?

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No I would leave it now you've done the stickers - maybe get some MicroMesh for next time if you fancy doing another hard shell, it really is the secret :)

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