Spraying in cool/cold weather.

[silly moo]

I asked a similar question in August

https://www.ngaugeforum.co.uk/SMFN/index.php?topic=46151.msg583172#msg583172

I found Halfords paints quite tolerant of humidity, my problem seems to have been being rather impatient as regards drying times.

[Steven B]

I've found humidity to be more of a problem than temperature - spraying outdoors (aerosol or airbrush) on a humid day can lead to poorer paint finishes than cold temperatures in my experience.

I've quite happily taken a warm model, with warm aerosol paint outside in near freezing temperatures, sprayed an undercoat and then brought everything back inside to dry without any problems.

Make sure the aerosol and model are warm (i.e. keep them in the house), and that you've given the paint a good mix/shake. Once you've done that, shake/mix it some more. Take the paint and model to your shed and paint.

Don't leave the model in the cold to dry. If you can't have it in the house then make a warm box for the shed - a cardboard box with a few hot water bottles or a seed tray heater will give it a nice cosy environment for the paint to go off.



Steven B

[weave]

Hi emjaybee,

Steven B beat me to it. Agreed, as in I reckon as long as the paint can and what your painting are room temperature it won't matter where you do it. Drying time is the problem but Steven B has a great solution. If not, it tends not to stink so much after a few minutes so you might be able to sneak it back in to a ventilated room somewhere away from your good lady.

Cheers weave 

[njee20]

Heating the paint makes the biggest difference IMO. I've been spraying quite a bit lately with Halfords cans, and I just put the can in a jug of warm water for 10 minutes before hand, if the can is warm to the touch there's a marked improvement in the viscosity of the paint, which tends to come out a bit thick if you do it in the cold.

If you take a warm model outside to spray I'd be worried about condensation forming, I leave the model in the cold, and haven't had any problems.

That said I bought some of the Halfords enamel sprays and they're proving quite poor, can't decide if they're just a bit rubbish or if that's temperature related!

[geoffc]

I agree with @njee20 heat the can in hot water. To keep the model warm before and after spraying, line a cardboard box with kitchen foil shiny side out, cut a hole in the top and shine a desk lamp through the hole. This method was recommended to me when I had problems resin casting due to the cold and damp.

Geoff

[Paddy]

May be that was the problem I had with the Humbrol cans i.e. too cold.  I will give the warm water a go next time.

Many thanks

Paddy

[honestjudge]

The problems I've found with any spray cans in temperatures below 20c is that clear varnish (any finish) will bloom as mentioned before, it will look hazy. Colours will dry incorrectly giving an orange peel finish i.e bumpy.
Just my experience, learning the hard way.

[emjaybee]

Been a busy day, so just getting back to it.

Thanks for all the info, some good ideas there. I'll go with the warming up the rattle can prior to use and then into a 'warm' drying box in the workshop.

I'll have to give it a go on a trial piece. The next item in the queue is the 40T bogie hopper wagon with the rivets, and I really DO NOT want to screw that up.

I'll keep you all posted when I get some results.

Thanks again for allthe feedback.

[Karhedron]

Blooming is mostly caused by moisture in the atmosphere. Cold damp winter days are the worst for spraying varnish. Moisture in the air gets caught in the spray and makes it go cloudy as it dries. I do a lot of wargames modelling and I have had more than one nice model ruined because I was impatient and rushed to get it varnished rather than waiting for a properly dry day.

Halfords lacquer is fairly tolerant but if you do not want to wait for warmer weather, at least wait until it is a dry clear day.

[emjaybee]

I have a 250watt heat lamp on order, the plan is to fit it in the angle poise lamp that hangs down over my work bench. I'm hoping it'll provide a warm 'envelope' over the work area whilst I spray from a warmed can onto the model.

Any feedback on this theory is welcome.

@Karhedron where have you been bloke, I have seen anything from you in a while. I hope all is good. Thanks for the info.

[Karhedron]

@Karhedron where have you been bloke, I have seen anything from you in a while. I hope all is good. Thanks for the info.

I have just been busy with family stuff mostly. The kids are growing up so more time spent with them and taking them to their various activities. I don't really mind, they are growing up so fast I don't want to miss stuff. The trains will always be there waiting to come out of their boxes but they will only be young once.

On a slightly less positive note, my mother-in-law moved to be near us about 3 years ago but her health took a turn for the worse last year so that is another priority call on our time.

I have been spending some time on Warhammer modelling lately as the 2 boys are really into this now. Here is my latest creation! Not really the sort of thing to have stomping around on my GWR BLT (unless I am modelling War of the Worlds or something ).

[emjaybee]

Ah yes, life gets in the way of so much.

I don't know what the model is, but it's pretty darned impressive.

[Karhedron]

I have a 250watt heat lamp on order, the plan is to fit it in the angle poise lamp that hangs down over my work bench. I'm hoping it'll provide a warm 'envelope' over the work area whilst I spray from a warmed can onto the model.

Any feedback on this theory is welcome.

That should work (I think). The crucial point is not so much the amount of moisture in the air but how saturated it is. Cold air can hold less moisture so tends to be closer to its saturation point. This is why moisture condenses onto windows etc at night when temperature drops.

Creating a warm pocket of air around your spraying area will decrease the percentage by which the air is saturated. This will make it less likely that the moisture in the air will condense out in the stream of varnish.

Please note that this is all theoretical. I would test it on something expendable first to be on the safe side.

[emjaybee]

Thanks for the feedback, I'll try it out on something less crucial than the hopper wagon that I'm decaling with a gazillion rivets!

[emjaybee]

Ok!

So today I thought I would test a method that would allow me to spray in the cool/cold weather were having.

The aim was to test two things.

Firstly, how the spray goes over the Railtec decal rivets.

Secondly, and more importantly, if I can get the same good spray results that I got in warm weather.

Taking on board suggestions from fellow forum members this is my process.

The spray can was stood in hand hot water for a good ten minutes. Whilst this was warming the test piece was placed under one of my drying covers and placed in the spray booth (cardboard box) with a 250w heat lamp about a foot away. The idea being to warm the workpiece up and create an 'envelope' of warm air around it.

Now the can was nice and warm, shake well and spray as normal keeping the workpiece in the warm air 'envelope'.

Once done, the workpiece was put back under the drying cover and back in front of the heat lamp.

The lamp seems to make the air inside the cover nice and warm without a hot spot.

This is the end result.



It's got good even, fine coverage, even matt finish and no 'bloom'. Very pleased with the result so I'll attempt a similar thing tomorrow with the wagon.

Wish me luck!