Humbrol enamel drying time

essdee
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Humbrol enamel drying time

Postby essdee » Sat Apr 23, 2016 8:23 pm

Yet more exciting discovery in the world of paint.....

I returned to a loco body, stored in a tupper box, to add the second brushed red Humbrol enamel coat to the buffer beams; the paint was slightly thinned with white spirit first for better flow around buffer stocks.

It soon became clear that the first coat (over Phoenix Precision two-part etch primer) had not hardened, and brush action soon 'removed' it.

My understanding was that enamels hardened with time, and this had been left in a central-heated upstairs room for five weeks.

How many months do other users of Humbrol 'enamel' leave it to harden, before it is safe to apply another coat, please? Many thanks.

Best wishes,

Steve

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Will L
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Re: Humbrol enamel drying time

Postby Will L » Sat Apr 23, 2016 9:39 pm

I think your problem may be using "white spirit" as a thinner. Some grades, typically turps substitute, aren't very volatile and leaves an oily residue. Better use the enamel thinners sold for the job.

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Flymo748
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Re: Humbrol enamel drying time

Postby Flymo748 » Sat Apr 23, 2016 10:19 pm

Another issue could be that being sealed in a tupperware box, the thinners have nowhere to go as they evaporate off the model.

Whilst I also use a "drying box" to keep the dust off, I do place the lid slightly askew so that air can circulate slightly. In my case it is a Really Useful Box, so the lid can sit a little higher and still prevent dust falling directly on the model.

HTH
Flymo
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www.5522models.co.uk

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James Wells
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Re: Humbrol enamel drying time

Postby James Wells » Sat Apr 23, 2016 10:58 pm

I use Humbrol extensively and never have problems like this. I doubt that white spirit is the problem - I use cheap white spirit for thinning for brushing and air brushing with no issues.

Was the model in a sealed container?

John Palmer
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Re: Humbrol enamel drying time

Postby John Palmer » Sun Apr 24, 2016 1:26 am

Post #50 in http://www.rmweb.co.uk/community/index.php?/topic/72228-humbrol-matt-enamels may be of interest, suggesting that current health and safety legislation has brought about a ban upon the use of volatile solvents on which paint makers used to rely to aid drying, with the consequence that it can be hard to get any enamel paint to dry these days.

I came upon this after a bit of internet research prompted by David L-T’s post in my own thread on this forum about problems with paint not drying (http://www.scalefour.org/forum/viewtopic.php?f=17&t=4798). What I find particularly worrying is the variability of people’s experiences. For example, some people find that paint from the same tin dries matt on one day and gloss on the next, others assert that they’ve never had any problem with Humbrol paint (witness James Wells’ post in this thread). I don’t mind if a particular product is identified as having as problem, as I can evade it just by not using the product concerned. But I despair when I hear that you can get erratic results from the same tin; seems like I’m playing Russian roulette with a model every time I open a pot.

Steve, your particular problem sounds suspiciously similar to the problem with Ferrari Red David L-T reported in the post referred to above in the thread I started. I hate to have to say it, but it may be a case of breaking out the paint stripper to remove the non-drying Humbrol red.

One solution I’ve seen suggested for dealing with paint that is expected to be reluctant to dry is to add a small quantity of Rustin’s Terebene paint drier to it. It’s not something I’ve been able to try, so if anyone has experience with this product I for one should interested to hear their views on it.

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David B
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Re: Humbrol enamel drying time

Postby David B » Sun Apr 24, 2016 6:11 am

I agree with Paul, that the problem is keeping the model in a sealed container.

When I have a painting blitz, to keep dust off the models I keep them under a propagator top (designed to fit over a large seed tray), one which has adjustable vents in the top, which I prop off the bench with pieces of card so that air can just get in underneath. I put the models inside after I have cleaned them and only take them out for spraying. When I have sprayed a model, I open the vent a very small amount but otherwise keep it closed.

My propagator top is years old but you used to be able to buy them at any garden centre.

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jim s-w
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Re: Humbrol enamel drying time

Postby jim s-w » Sun Apr 24, 2016 9:10 am

I've found in recent years that the quality of humbrol paint has dropped quite significantly. The coverage is far worse, the way it dries is different and some of the colours are nothing like what they used to be (as well as the colour shown on the lid).

Jim

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Noel
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Re: Humbrol enamel drying time

Postby Noel » Sun Apr 24, 2016 10:28 am

Other factors may have had an influence, but I would agree that keeping the model in a closed container is most likely the problem, especially if the container was small. Paint drying results from the evaporation of the solvents within it, but the air within the container can only contain a certain proportion of solvent. If more solvent is available in the paint than the air can contain, evaporation will effectively cease.
Regards
Noel

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James Wells
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Re: Humbrol enamel drying time

Postby James Wells » Sun Apr 24, 2016 11:00 am

jim s-w wrote:I've found in recent years that the quality of humbrol paint has dropped quite significantly.


I don't have problems like this, but I tend to scope out the pigment and mix it with white spirit! It may be the carrier has changed rather than the pigment?

Given how long it may take for a shop to sell enough of some colours before they need to reorder, the age of some tins on sale could be an issue.

A couple of years back I bought six tins of Brown Bess (Ian Fleming's favourite!) which hasn't been around for a number of years! Old paint in some cases could cause problems in some instances.

essdee
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Re: Humbrol enamel drying time

Postby essdee » Sun Apr 24, 2016 11:25 am

Thanks guys for the responses above, much appreciated.

Firstly, I must removed one possible source for the problem; the 'sealed container'. My reference to a tupper box obviously suggests a sealed container; I even erred in using 'tupper' - it was in fact an ice cream container, with the lid loosely placed to reduce dust invasion - although I use cellulose as the main body paint (after separate problems which have already seen Humbrol gloss, satin and matt black paints consigned literally to the bin). My apologies for leading you astray there - and I take note of that warning about sealed containers for the future, an excellent point.

Secondly, the paint is Humbrol satin red No. 174, bought in town about six weeks ago, with the 'made in UK' & Union Jack on the tin. I stand behind Jim on this one.....

Will's and John's replies illustrate the classic problem of 'solutions' that in themselves seem to vary depending on who is applying them! I checked back to Ian Rathbone's book, and it seems that five weeks should be more than ample for enamel. I followed Ian's recommendation also in thinning using white spirit.....

The bright side of this is that clearly I can use white spirit to remove the recent and 5-week old Humbrol 'paint' applications, without affecting the cellulose-based etch-primer on the buffers and beam?! Incidentally, Will, it had all the appearance of a matt-satin finish and initially took the second application fine; it was only when I returned to overlap brush strokes that the problem arose -ie. the fresh, thinned, paint had already softened the original coat.

Any suggestions as to an alternative to Humbrol for a buffer beam red -I will now not touch it at all? I am tempted by eg. Tamiya acrylic, but I do not have experience of acrylics and I wonder also how that would react to Testors Dullcote lacquer, which I have now got to behave as I would like.

Meanwhile, back to the more rewarding joys of the garden.....

Thanks again chaps, all best,

Steve

essdee
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Re: Humbrol enamel drying time

Postby essdee » Sun Apr 24, 2016 3:13 pm

Further to the above, I have done some experimentation - having also noted that the patch of thinned red Humbrol paint in the tin lid remained tacky, exposed to air, 16 hours after mixing. Admittedly, it was a cold night last night.

As suspected, a sable brush with Wickes white spirit (no mention of turps substitute on the recipe) soon drew off all the second coat, and the thinner parts of the first coat, leaving a thicker residue gathered in the angle of buffers and buffer beam, to leave the cellulose base layer.

I have similarly thinned some more red paint with Humbrol brand thinners, bought at the same time as the paint recently, and applied to half of a test piece primed buffer plank, with the remainder painted in unthinned red paint, drawing off excess paint to leave a brush-free finish, as near as possible. I will leave these exposed to the air in a centrally heated room from 4pm today and see what happens. I also left a patch of the Humbrol-thinned paint next to the white spirit-thinned patch on the Humbrol tin lid, to compare how dry it is tomorrow.

Will report back!

James W. - that's an interesting idea; once this paint has settled out again, I will try your method of extracting pigment to mix with white spirit. I presume you are thereby avoiding the rather 'glutinous' finish that seems to affect Humbrol red paints? Thanks!

Thanks again all, for the input,

Best wishes,

Steve


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