HELP!! What am I doing wrong

[mth]

Hi All
I'm trying to repaint a Hornby Dublo A4.
Both attempts have failed with paint and primer lifting off when de-masking.

To paint I cleaned the model in worm soapy water and gave a good scrub with cream cleaner using a tooth brush. Model only handled from this point with gloves on.
When dry I then wiped the model with thinners to get rid of any grease left.
Sprayed on Halfords etch primer. Left to dry for 48 hours.
Air brushed the railmatch paint. again left to dry for 48 hours.
Masked and whilst adjusting the Tamya tape a large patch of paint and primer lifted off.

What am i doing wrong.

 

[Norman Clymer]

Masking tape is best removed as soon as painting is completed and before the paint hardens.

 

[Joe's Garage]

I believe Halfords paint is acrylic so forms a plastic skin, mention of the tape pulling the primer off too indicates a less than adequate "key" for the paint perhaps.
I'm no expert on painting but hopefully someone will be along. Calling Larry G??
Also does the soap contain any oils or such like that prevents the key for the paint?
Good luck
Julian

 

[mth]

I believe Halfords paint is acrylic so forms a plastic skin, mention of the tape pulling the primer off too indicates a less than adequate "key" for the paint perhaps.
I'm no expert on painting but hopefully someone will be along. Calling Larry G??
Also does the soap contain any oils or such like that prevents the key for the paint?
Good luck
Julian

The 'soap' is 'Flash'. I was warned about washing up liquid some years ago. I've had no problems with other metal models just this one.

 

[mth]

Masking tape is best removed as soon as painting is completed and before the paint hardens.

I agree with you on that one, but the issue arrived when i was masking up the model for the next colour.

 

[jonte]

You could try Acid Etch Primer available in aerosol form from the likes of Halfords, and then spray the primer on top.

Should provide a good key for the primer and paint.

 

[GrahamMc]

Interesting question. I have a Liquitex guide for acrylic artists, (Liquitex. The acrylic book.) Liquitex being one of the companies to be an early producer of acrylic paint. Their advice is that plastics don't need an undercoat or primer but they warn that some plastics, if smooth will repel acrylic paint making it easy to peel off. Their answer is to sand it, give it a key, not very practical in your case?
On RM web there is advice that suggests military modellers solve this problem by giving the job a coat of PVA. That might be worth looking into. Could it be that plastic 'primers' are glue? No idea, but hope this might be a starting point for you.

 

[Osgood]

The problem appears to be the inability of the primer to adhere to the original Hornby paint.
So if you knew what type of paint the original Hornby paint is you might be able to select an appropriate primer?

 

[76043]

I've only repainted Dublo items by stripping the original paint first. Then used Halfords primer as you did, but then didn't mix and match paint types. I believe Railmatch is enamel? It does take several days to harden, this might be the issue I think especially if after 48 hrs you can still smell the enamel.
Tony

 

[PhilH]

Try abrading the original paint, slightly roughening the surface to give a key. You could use an abrasive pad or very fine wire wool, or (very gently !) a glass fibre brush.

 

[Dave F.]

Does the 'Flash' cleaner contain lanolin to give the surface a shine which can stop paint adhering.
I use 'Mr Muscle Bathroom Cleaner' and never had any problem.

Dave.

 

[jonte]

Respectfully, fellow WT-ers, I think you’re getting ahead of yourselves here.

From what I can gather from the author’s original post, it’s not just the paint that’s lifting but the primer too, so it’s the lack of key to the metal surface where the issue lies I would suspect, hence my suggestion re the Acid Etch.

Despite the type of rinsing method used, once the thinners has been applied then left to dry, it should be good to go.

My advice is to go back to bare metal and start again.

Incidentally, I’ve found Dettol an excellent paint remover in the past, but I recall my good friend @Lyndhurstman enjoying excellent results recently with regard to paint stripping, so perhaps if you get the link, Jan, you might be able to suggest?
Apologies, Jan, but my memory isn’t what it used to be

Jon

 

[Fitzroy]

Was it bare metal to start with, and if it was, was the metal bright or was it coated with a thin layer of 70 year old zinc oxide? Any old original paint would be enamel, and bare metal if not sand blasted or rubbed with wire wool or scotchbrite or wet/dry will not be great for adhesion.

 

[mth]

Thanks all for the reply's.

Just to clarify the primer lifted from the body. I've now managed to remove most of the primer/paint with a strip of masking tape.

Was it bare metal to start with, and if it was, was the metal bright or was it coated with a thin layer of 70 year old zinc oxide? Any old original paint would be enamel, and bare metal if not sand blasted or rubbed with wire wool or scotchbrite or wet/dry will not be great for adhesion.

The model was stripped to bare metal for both attempts, cleaned and 'polished' with a mini drill wire wheel. I will give scotchbrite a go.

 

[Lyndhurstman]

Respectfully, fellow WT-ers, I think you’re getting ahead of yourselves here.

From what I can gather from the author’s original post, it’s not just the paint that’s lifting but the primer too, so it’s the lack of key to the metal surface where the issue lies I would suspect, hence my suggestion re the Acid Etch.

Despite the type of rinsing method used, once the thinners has been applied then left to dry, it should be good to go.

My advice is to go back to bare metal and start again.

Incidentally, I’ve found Dettol an excellent paint remover in the past, but I recall my good friend @Lyndhurstman enjoying excellent results recently with regard to paint stripping, so perhaps if you get the link, Jan, you might be able to suggest?
Apologies, Jan, but my memory isn’t what it used to be

Jon

Hi @jonte
No worries. Memory is a tricksy business as we get older. I was lying in bed trying to remember the name of an actor last night. I remembered it, but have since forgotten why I wanted to recall it
The stuff is Kling Strip. The post is here 4mm - Jan's 4mm WB: Leverage It's very good, in my opinion, and provides a bare metal finish without whiffery.

Cheers

Jan

 

[Richard Gawler]

The model was stripped to bare metal for both attempts, cleaned and 'polished' with a mini drill wire wheel. I will give scotchbrite a go.

https://www.halfords.com/motoring/p...primer/halfords-etch-primer-500ml-370400.html

Some reviews of the Halford own-brand etch primer claim that the product does onto adhere to aluminium . . . I wonder if the Hornby Dublo die-cast metal is causing it problems.

I suggest try U-POL number 8. I am on my third can and so far it has worked with everything, even some plastic when I forgot to mask it.

 

[sagaguy]

Never use washing up liquid or any lanolin based detergent,paint will not stick to any casting washed with these products.I`ve always used cif or supermarket cream cleaners,these have a slight etching effect due to the citric acid in the formula,a final rinse with hot water and you should be good to go.I`ve always repainted HD and other locos using this method of a grey acrylic primer and acrylic paints such as halfords finishing with railmatch enamel satin varnish to protect the transfers.Below,a conversion of the Ivatt coronation,the most difficult transferring job i had ever attempted.

Ray.

 

[jonte]

Never use washing up liquid or any lanolin based detergent,paint will not stick to any casting washed with these products.I`ve always used cif or supermarket cream cleaners,these have a slight etching effect due to the citric acid in the formula,a final rinse with hot water and you should be good to go.I`ve always repainted HD and other locos using this method of a grey acrylic primer and acrylic paints such as halfords finishing with railmatch enamel satin varnish to protect the transfers.Below,a conversion of the Ivatt coronation,the most difficult transferring job i had ever attempted.

Ray.View attachment 231338

Another Cif user here.

 

[jonte]

@mth :

Funnily enough, I watched a video the other day by a modeller going by the username of Dusty Shelf Collectables who stripped and repainted a Dublo A4(?) to wartime black. I’m not sure whether it will be much help here as the only part of the process shown is the stripping of paint (although I’m sure I can see signs of residual paint on the surface), after which he goes on to show it in its final paint form.

It a two-part vid, but I’ve only posted part two as this pertains to the matter in hand, and can be seen from approximately 2 mins 50 secs in:

As I say, I’m not sure whether if it’s of any help, but it just struck a chord.

Jon

 

[Osgood]

Another Cif user here.

The appropriate Authorities have been notified.