Two-pack etch primer falls off brass model

[47137]

Hi,

 

I cleaned a brass model using a cellulose synthetic thinner PQ17, then brushed on one coat of a two-pack primer sold as PQ32 and PQ31. This was very thin, so I applied a second coat the next evening (about 24 hours later). The first coat curdled up wherever I touched it with the brush, I left it to 'cure' so I could rub it down. Now, four days later, I can remove the primer using a finger nail and water.

 

What do I need to do to make this stuff work? I have never used it before.

 

For info, I mixed up about 5 ml, using a 2.5ml spoon. Quite a small quantity, and the mix was probably not exactly 50:50. Temperature was about 17 deg C.

 

Thanks,

Richard.

 

[Ian Fisher]

No idea why your mix didnt work.

 

I would look to give it a rub down with some fibreglass see if that may remove any grease and may just provide a key.

 

Worth thinking is using halfords primer no need to mix give it a shake and spray, also worth a try is using an ohp pen on edges that may see heavy traffic, extra cover if any paint does get rubbed or knocked.

 

Ian

 

Edit to the person who disagreed with a post thats over a year old but not seemingly added a fix or insight why diasgree with just one post? Sorry I dont get the motive..its a fix and good practice.

Edited June 2, 2014 by Ian Fisher

[Miss Prism]

Whose products are we referring to?

[meld]

Whose products are we referring to?

Miss P

 

The Product Numbers would Suggest Precision Paints.

 

Mike

[47137]

Miss Prism: as Mike suggests, the thinner and paint are from Phoenix Precision.

 

Ian: I have some Holts acrylic primer, I will try this on some scrap brass. I like the idea of an OHP pen.

 

On the bright side, I have stripped the model very easily.

[shortliner]

Google suggests http://www.scale-models.co.uk/engineering-tooling/5295-keying-brass-prior-painting-loco-chassis-parts.html

[R A Watson]

That primer is only supposed to be used as a single thin coat to allow a normal coat of primer to stik in the normal way on top of it!

 

Trying to apply a second coat will only soften and release the initial layer as you have found out.

 

Wally

[alfsboy]

I used Halfords  or Hycote grey or white primer on virtually everything I have made for the last 30 odd years what ever its made of .On plastics like styrene I dont  flood the paint on as its the thinners in the paint that attacks plastic but its OK on ABS types .It stays on remarkably well .If a loco is black I use the same make of matt or satin as well .i have mainly done US brass locos and resin or metal racing cars and some figure painting .Its also been used on etched brass locos and white metal .

[darren01]

HI

Have you heard of this stuff,works very well and gives a good coat ,I have used it on my High level loco and gives the paint a amazing finnish.

It sticks to brass like glue!.

U-POL POWER CAN GREY ETCH PRIMMER £4.49.

Hope this helps

Darren01

[47137]

I

That primer is only supposed to be used as a single thin coat to allow a normal coat of primer to stik in the normal way on top of it!
Trying to apply a second coat will only soften and release the initial layer as you have found out

Wally, this is an important point and I can only plead ignorance, the instructions mention 'top coats' but there is no mention of using conventional primer nor your single-coat rule. I saw it soften, but imagined it would set again.

 

I had splodged some primer onto an unprepared bare brass fret last weekend, this stuck well ... indeed I cannot scrape it off. This tells me the mix was good, but second application and possibly the surface preparation was wrong. I had cleaned the surface with only PQ-17. I have now cleaned the model with white vinegar, then a glass fibre brush, then PQ-17, then the fibre brush again. Wet and dry seemed a bit harsh. Working in daylight I can see the PQ-17 evaporates quickly but leaves a residue on the surface. Hence the second working with the fibre brush. I have today made a fresh mix, this time about 55% primer / 45% thinner in an attempt to make it more brushable, 'painted' it onto the model and left it to harden. Tomorrow will tell.

 

Meanwhile ... the Holts acrylic white primer stuck well on a flat surface but rubs off easily on sharp edges. It will be my second coat (tomorrow), unless someone steers me towards a different route! I will look out for the other products everyone has suggested.

[47137]

Well, my second attempt with the PQ32/31 was sort of less unsuccessful than the first. This evening (30 hours on), the primer easily rubbed off the top and one side of the bonnet (just like a lottery scratchcard), but held firm elsewhere. I can only conclude I have a modelling hygiene problem. Patience ended, I cleaned the bare areas, again, and applied three coats of the Holts acrylic primer all over.

 

If we have an 'innovations' competition this year, I know what my suggestion will be ... for manufacturers of etched brass kits to put a base primer on the 'outside' face of the parts! Somehow I suspect small/medium batch production using an industrial metal cleaner or shot blasting, a larger volume mix and a controlled spray application has a better chance of success than me.

[Ian Fisher]

Sorry to hear your troubles persists.

 

Having never used a two primer, I feel my simpler route of halfords all purpose grey primer must work for a reason!

 

Well worth the fiver or so, lasts ages and sticks like wotnot to a blanket.

 

As for cleaning any further residue if possible a dunk in some boiled water can get rid of any further nasties.

 

Goodluck

 

Ian

[N15class]

It does sound like dirty brass. I like to give my models a good scrub with a powder cleaner like vim or barkeepers friend. Then another good scrubing with viacal. This seems to work for me. I also keep away from glass fibre brushes nasty little things,bit get left everywhere including in your fingers, use the brass refills instead.

[halfwit]

Has the paint got a use by date on it? Phoenix Precision aerosol etch primers, which I use with no problems, are time sensitive, I'm not sure about the tinned stuff.

 

If I'm not mistaken that's an A1 Models kit, which should be fairly new, so dirty brass shouldn't really be a problem.

 

I always clean brass with Cif followed by cellulose thinners before etch priming. Normal primer is then applied.

[47137]

Has the paint got a use by date on it? Phoenix Precision aerosol etch primers, which I use with no problems, are time sensitive, I'm not sure about the tinned stuff.

 

If I'm not mistaken that's an A1 Models kit, which should be fairly new, so dirty brass shouldn't really be a problem.

 

The paint is 'jarred' rather than 'tinned' so to speak, there is a use by date but it is around 5 years from now. I am sure the problem is grime or grease, and it is my fault. It is indeed an A1 Models kit (their p/n A18), but put together with sloping bonnet sides and grill onto a different body/chassis ... and I fiddled around a lot while I worked out what I wanted it to look like. It is a good kit for a beginner. I will post another pic when I finish it.

[halfwit]

I wonder if the 'residue' that you saw on the surface after cleaning with cellulose thnners is the problem? Does anyone know if PP cellulose thinners are different to other brands?

[sleeper]

Forgive my ignorance but what is an OHP pen?  Perhaps someone could enlighten me as to what it is and where you can obtain one.

My only thoughts on the problem in this thread is on the use of cellulose thinners prior to the etch primer. Halfwit has said he uses this process with success but I wonder if he uses Precision Paints etch primer or some other brand. Another possibility is that there is cellulose paint thinners and cellulose gun cleaner, a lower grade thinner, could that be a contributing factor?

[halfwit]

...My only thoughts on the problem in this thread is on the use of cellulose thinners prior to the etch primer. Halfwit has said he uses this process with success but I wonder if he uses Precision Paints etch primer or some other brand...

 

Phoenix Precision PQ1 aerosol grey etch primer and Stevens cellulose thinners to clean.

[craigwelsh]

Forgive my ignorance but what is an OHP pen? 

Over head projector I think.

 

Metal blackening pen is an alternative.

[Ian Fisher]

Yep OHP, is Overhead or any wiffy markers really, you can get a good range of colours too if you have access to a good art/graphic shop.

 

And yes blackening pens are another option if you want it "black".

 

Ian

Edited May 1, 2013 by Ian Fisher

[mozzer models]

I use halfords spray primers & have done so for 8 years not had any problems to date

[47137]

Here is a second photo to finish the thread off. The 'white' is Holts primer - this seems to dry matt if you just dust it on, but with a slight sheen after a heavier coat. I have never had a white engine before, but it seems to suit! I now have some aerosols of U-Pol 'Acid no.8' and Halfords grey primer no. 473116, but these will have to wait for a future model. Halfords range of primers was a bit overwhelming, but I am guessing this one will be suitable for most materials. Thanks again for all the ideas, Richard.

 

[cunninji]

Hi All,

I hope this explanation will help others.

 

I am in the midst of my first major paint modelling project to recreate the 1937 Coronation Scot train; it is now progressing well bit plenty of snags on the way! In the past I have only needed to paint brass signals (so brush painting was fine) but now I am painting Comet coach bodies with Aluminium roofs and Brass sides and I need to use an airbrush to achieve the finish I am looking for. I have spent some time searching forum and struggled to get a clear steer on airbrushing with etch primer. I finally found the answer in the Right Track DVD series (part 3) and talking to an experienced painter at an exhibition. 

 

In my experience, brush painting Phoenix etch was fine both 1 part and 2 part but I really struggled with airbrushing Phoenix 2 part - it would cobweb and wouldn't stick. This is confirmed in books that I have read but the answer wasn't included! I can't get on with aerosol - Phoenix do one. I can't control the flow and I end up with runs on the model - it does stick though! I recommend the book by Ian Rathbone (Painting and Lining). He has a recipe for airbrushing with Phoenix 2 part that actually works! 1 part paint, 2 parts acid activator and 1 part cellulose thinner. The extra acid presumably improves the etching/adhesion power and the cellulose thinner helps the flow and stops the cobwebs! Cleaning the model is very important. For metal models, wash in an alkaline solution (such as flash) to neutralise solder flux, rinse throughly with water, leave to dry (a hairdryer can speed the process) and then degrease using cellulose thinners (plenty of ventilation and don't breath the vapours; I wear my respirator when doing this stage). Don't use cellulose thinners on plastic. Degrease plastic models with white spirit.

 

Incidentally, I have seen something on RMWeb suggesting that etch primer is designed for steel which is nonsense. Etch primer is designed for ferrous and non ferrous metals. Phoenix 1 part is non ferrous and 2 part is ferrous and non ferrous. Stainless steel won't etch which is why I have doubts about the advice that you need to reserve an airbrush for etch primer (but I do so just in case!).

 

I hope this helps!