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Railmatch/Humbrol outgassing time


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Bit of a disaster today wafting some Humbrol acrylic matt varnish over a model painted with enamels, this photo after I rubbed down the worst with some wet and dry paper:

post-14389-0-92289000-1545074118.jpg

 

The model had three coats of Halfords primers a week or so ago. A coat of grey, some Revell Plasto filler then two coats of white.

 

Then three days ago I brushed on a top coat of Railmatch "Faded BR Blue" but this came out turquoise so the next day I stirred in some Humbrol enamel matt blue and did another coat, and then a third coat yesterday. This actually looked quite good, really the only thing to detract was my vertical brush marks which looked like brush marks and not the rain staining I had hoped for.

 

Well ... I have read, you must let enamel paints not just dry but cure as well before overcoating with acrylic ... and clearly the 18 hours I allowed from yesterday to today was not enough. I wonder, what would be a sensible time to wait?

 

- Richard.

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Bit of a disaster today wafting some Humbrol acrylic matt varnish over a model painted with enamels, this photo after I rubbed down the worst with some wet and dry paper:

attachicon.gifDSCF8727.jpg

 

The model had three coats of Halfords primers a week or so ago. A coat of grey, some Revell Plasto filler then two coats of white.

 

Then three days ago I brushed on a top coat of Railmatch "Faded BR Blue" but this came out turquoise so the next day I stirred in some Humbrol enamel matt blue and did another coat, and then a third coat yesterday. This actually looked quite good, really the only thing to detract was my vertical brush marks which looked like brush marks and not the rain staining I had hoped for.

 

Well ... I have read, you must let enamel paints not just dry but cure as well before overcoating with acrylic ... and clearly the 18 hours I allowed from yesterday to today was not enough. I wonder, what would be a sensible time to wait?

 

- Richard.

 

I don`t know how long to cure paint, but the effect that it has had looks pretty impressive of flaking paint of an old vehicle or structure, it reminds me of some of the stock awaiting restoration on preservation sites

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I do like the idea of representing faded and peeling paint, but I think it is a bit coarse (overscale) as it happened here. Maybe try a test piece leaving six hours between the enamel and the acrylic, see what happens. It would look good with a grey undercoat showing through.

 

Anyway, I have a plan. I applied one new top coat yesterday and this has not disintegrated. I'll try a second coat this evening. Put some paint on scrap plastic too. Try the acrylic varnish on the scrap at the end of the week.

 

I will report back.

 

- Richard.

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I find Dettol work well for removing paint. Cheap, doesn't damage the plastic & removes factory paintwork too.

You'll be down to the bare plastic but at least you can start again.

I remember speaking to someone years ago who resprayed locos for customers. He left it a week between coats for the paint to go hard.

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Pete - I have allowed myself one more top coat, I brushed this on today. I am beginning to lose detail around the doors now and I cannot add any more paint, but it must be worth a try if only because it will save so much time over going back to the bare plastic. I've bought a bottle of Dettol for future use and I can experiment with this on scrap models.

 

Andrew - there is no decent reason at all. I think, cutting corners like using acrylic varnish over enamel "because I have some acrylic to hand" may be ok for experts but it's not a good way to evolve technique. I'll buy some enamel varnish, I can use it on another model I painted a few weeks ago too.

 

I'm not sure about sensing a smell of curing paint but I understand the idea.I couldn't smell anything from yesterday's coat before I started today.

 

- Richard.

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I advise waiting 48 hours for airbrushed enamels to dry hard before putting anything over the top. If you've applied enamels using a bristle brush then it ought to be longer because the coat will be thicker. I think the problem you are having is caused by time (not enough) and paint (too much).  :nowinkclear:

 

Although acrylics dry much quicker they still need to be hard before working over them, probably 24 hours to be safe.

 

When needing a barrier between different materials, such as pigment and gouache or enamel and artists oils, I apply a coat of Testor's Dullcote to separate them.

 

Personal opinions based on experience. Other opinions are available.

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I have made some very bad mistakes with paint in the past . 

 

These days I cut a bit of something like foam board or plasticard about 3 "  by a couple of foot long . I spray the foam board with primer , leave it , If ok I prime the model. Then I spray 6 '' of the  the foamboard with the model colour. If its ok ,I spray the rest , if not , next 6" gets sprayed till I'm happy , then the model . 

 

Next a sample of the other oversprays or hand paint colours. when dry I look at it carefully,  if not happy do more , if ok , do model. 

 

Then transfers, try them on the foamboard if ok, do model . Then some lining. 

 

Finally varnishes. Do the foamboard bit by bit, if not try a different one . See if it is ok with the lining and transfers. 

 

I know this sounds like a longwinded method but I am lost with modern paint chemistry. Paints are just not what they used to be and I can't keep up. I would agree with the above comments about time , a couple of days at least between coats. Longer if its wet weather, RH seems to affect it.  My only real advice here is do a test sample first and label them , I am slowly making up a load of these test samples to help me.

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Shame you didn't use red primer as it would have looked like rust

Looks like it melted the plastic. Probably best to stick with enamels or stick with acrylics. What was the primer, acrylic or cellulose?

It looks like the effect I got putting enamel on Poundland primer, and no I don't know if that is cellulose or acrylic.

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The primer was acrylic, there is no cellulose paint in my armoury nowadays. But I've clipped the model together this morning in an act of defiance, and I think the overall effect will be adequate for my layout after I've done the gangway ends. It's come a long way from the original shells.

 

- Richard.

 

post-14389-0-52696300-1545212581.jpg

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I have made some very bad mistakes with paint in the past .

 

These days I cut a bit of something like foam board or plasticard about 3 " by a couple of foot long . I spray the foam board with primer , leave it , If ok I prime the model. Then I spray 6 '' of the the foamboard with the model colour. If its ok ,I spray the rest , if not , next 6" gets sprayed till I'm happy , then the model .

 

Next a sample of the other oversprays or hand paint colours. when dry I look at it carefully, if not happy do more , if ok , do model.

 

Then transfers, try them on the foamboard if ok, do model . Then some lining.

 

Finally varnishes. Do the foamboard bit by bit, if not try a different one . See if it is ok with the lining and transfers.

 

I know this sounds like a longwinded method but I am lost with modern paint chemistry. Paints are just not what they used to be and I can't keep up. I would agree with the above comments about time , a couple of days at least between coats. Longer if its wet weather, RH seems to affect it. My only real advice here is do a test sample first and label them , I am slowly making up a load of these test samples to help me.

Couldn’t agree more. Each time I get a good finish I dread the next one in case it all goes wrong. Particularly with rattle cans which seem to be very inconsistent. I think a standard test approach is the way forward.

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We really shouldn't dread painting, but I know I do too and I have many models still running around unpainted. I am frightened of spoiling them. Most often, I get passable even quite good results on scenery and structures, but below-par results on trains.

 

And so, although it is probably better for this model to strip and start again, it is probably better for me to accept it and move on. It will be too wearying to do it all again, get it a bit better but still not really good enough. When I get a system of painting in place which gives me a bit of confidence in the results, maybe I'll go back to it.

 

I have added a coat of Humbrol matt enamel varnish (aerosol), and it looks as though this will pull the model together so to speak, and hide most of my brush marks.

 

- Richard.

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I find Dettol work well for removing paint. Cheap, doesn't damage the plastic & removes factory paintwork too.

You'll be down to the bare plastic but at least you can start again.

I remember speaking to someone years ago who resprayed locos for customers. He left it a week between coats for the paint to go hard.

I've just used Dettol to strip the paint from a Roco wagon. It worked really well, and a lot easier to use than the stuff I bought in a model shop to do the same job. Cheaper too.

 

I was intrigued to see the model had been finished twice in the factory. After I got through the printing and paint, there was another set of printing on the bare plastic shell. It is as though Roco had some slow-selling stock, and gave it a new image. This is their track cleaning wagon.

 

- Richard.

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Couldn’t agree more. Each time I get a good finish I dread the next one in case it all goes wrong. Particularly with rattle cans which seem to be very inconsistent. I think a standard test approach is the way forward.

 

I've finally finished this model, thank you to everyone for all the help.

 

- Richard.

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