Model Boat Mayhem - Forum

Technical, Techniques, Hints, and Tips => Painting, Finishing and Care. => Topic started by: john44 on June 24, 2019, 10:12:44 AM

Title: Primer coat crazing in places
Post by: john44 on June 24, 2019, 10:12:44 AM
Hi guys, what causes a primer coat of paint to craze in places.it is a newly glassed hull
 sanded down as usual cleaned and primed with Halfords primer spray can.
The Simonise red primer below the waterline paint went on fine no problems {:-{

John
Title: Re: Primer coat crazing in places
Post by: imsinking on June 24, 2019, 10:31:30 AM
Halfords primer, IT'S CRAP  >>:-(  learned my lesson with it way back , the hi-build primer is the worst goes on lovely , rub it down, spray on final colour . . .  cracks all over the place . . . something to do with the double acrylic formula I believe , a scrape off job . . .
 I went over to TETROSYL products, first coat self etching primer x 3 ( must let these dry out properly), then normal primer and the final finishing colour , 4 boats so far paint is still good even on the first boat from 4 years back .
Bill 
Title: Re: Primer coat crazing in places
Post by: imsinking on June 24, 2019, 11:07:20 AM
Halfords primer, IT'S CRAP  >>:-(  learned my lesson with it way back , the hi-build primer is the worst goes on lovely , rub it down, spray on final colour . . .  cracks all over the place . . . something to do with the double acrylic formula I believe , a scrape off job . . .
 I went over to TETROSYL products, first coat self etching primer x 3 ( must let these dry out properly), then normal primer and the final finishing colour , 4 boats so far paint is still good even on the first boat from 4 years back .
Bill
CRAP maybe a strong word  %)  reacts with it's own spray overs might be more suitable . . .
Bill
Title: Re: Primer coat crazing in places
Post by: RST on June 24, 2019, 11:08:29 AM
Last 2 years Halfords paints do not seem to be the same as they were. They used to be great, now they're very variable, no consistency and don't dry the same. I'm having the same probs with krylon paints also -they used to be good.  No doubt some EU ruling on chemicals, all the paints seem to be going the same way downhill.
Title: Re: Primer coat crazing in places
Post by: KitS on June 24, 2019, 12:11:46 PM
I NEVER have problems with Halfords spray cans, and I've been using their Grey Primer and Appliance White since the 1980s.

And I can't say I've noticed any degredation in their quality either, but I've not used the hi-build primer variant.
Title: Re: Primer coat crazing in places
Post by: john44 on June 24, 2019, 12:39:36 PM
Hi, it was not the hi-build just ordinary primer


John
Title: Re: Primer coat crazing in places
Post by: RST on June 24, 2019, 12:59:50 PM
Last 3-4 cans of hi-build dried "ish" like rubber. Other cans of regular plastic primer have been crazing with just about anything on top. They've been a real pain for me, can't be a batch issue as there been quite allot of cans from a few stores. Halfords cans seem to be the same quality as the cheap pound store cans these days.
Title: Re: Primer coat crazing in places
Post by: Colin Bishop on June 24, 2019, 01:02:52 PM
I have been using all three standard Halfords primers, matt black and appliance white extensively recently and not had any problems. Very impressed with their matt lacquer too.
Colin
Title: Re: Primer coat crazing in places
Post by: TailUK on June 24, 2019, 01:22:10 PM
Hi guys, what causes a primer coat of paint to craze in places.it is a newly glassed hull
 sanded down as usual cleaned and primed with Halfords primer spray can.
The Simonise red primer below the waterline paint went on fine no problems {:-{

John

Halfords primer is commonly referred to as "acrylic" paint but it's more complicated than that.  Simonized also make a "acrylic" red primer. The base solvent for both of these is de-natured alcohol. so it should smell a little like meths when applied.  Simonized also make a red oxide primer that is acetone based (which usually smells like pear drops when applied).  Acrylic based and Acetone based are incompatible and will craze, wrinkle and on occasion, flake off when used together.
And the moral of our story is reduce the risk by ensuring that all the paint you use have the same base solvent.  Then you only have to worry about moisture, temperature, surface contamination and faulty tins.
Title: Re: Primer coat crazing in places
Post by: john44 on June 24, 2019, 08:20:52 PM
Hi guys, stripped all the Halfords (advanced acrylic primer) off the boat.
Re sprayed with autotek plastic primer gave a perfect finish.
So no more  so called advanced Halfords paint on my models.
I never spray heavy coats and always leave to dry for 10-15 min between coats.
2-3 coats if needed
Thanks for your input


John
Title: Re: Primer coat crazing in places
Post by: coch y bonddu on June 24, 2019, 09:01:10 PM
Paint Incompatibility 100% and defo far to thick coats


Dave
Title: Re: Primer coat crazing in places
Post by: john44 on June 24, 2019, 09:33:41 PM
Hi Dave, there was no other paint to be incompatible with the reaction was with itself.
I have definitely not applied to thick a coat I learned that lesson 30 years ago.


Regards


John
Title: Re: Primer coat crazing in places
Post by: Capt Podge on June 24, 2019, 10:34:21 PM
I've been using Halford rattle cans since 1997, primer, top coats & lacquer, and never had any issues on the 12 models built so far.
Depending on what the model is made from I use either 2 or 3 coats of primer, rubbing down between each application.
Works for me  :-))
Regards,
Ray.