How to paint an period fireplace

[sifly]

Hi,

Yesterday I removed the paint from an original Edwardian fireplace using Nitromors.

Today I used Crown Period Colours paint (for interior metals and wood) on the surround and mantle piece.

My problem is that when the paint dried, brown/rusty stains became visible through the paint - not exactly the look I'm after!

How can I stop this happening? Do I just have to put loads more coats of paint over or is there a specific primer to use?

Thanks for any help that you can provide.

 

[Zampa]

Im not familiar with the rang that much...but was it oil based or water?

 

[sifly]

Hi Zampa,

It is water based.

 

[Zampa]

Hi Zampa,

It is water based.

By putting water base stuff on metal you have started a reaction..

Bad news...it really should all come off again

 

[sifly]

aaaaaargh!

I went round a local hardware store who said the same thing. I have now removed the paint again and applied a metal primer they supplied. Hopefully it wont take too many coats to hided the reddish/brown colour of the primer.

Thanks for your help Zampa....I should have asked here first before starting!

 

[JohnD]

aaaaaargh!
Hopefully it wont take too many coats to hided the reddish/brown colour of the primer.

A grey undercoat will cover up the red oxide colour. If you want to paint it white, give it a white undercoat afterwards. Topcoats have less covering power than undercoats. Might be better to avoid water-based paints on old cast iron.

 

[sifly]

Thanks JohnD

Typically the paint of "our" choice is an off white. Do you think my wife does this on purpose?

So a grey undercoat followed by a white undercoat is needed. Are they labelled "Metal undercoats" or would any undercoat be fine now that the primer is on?

Is there a particullar brand I should go for, or more importantly, avoid?

Sorry for all the questions but I really don't want to make any more of a hash of this one than I already have

 

[JohnD]

Indoors, it shouldn't matter what undercoat you use (but get a spirit-based one, not water, you don't want to give that old iron an excuse to go rusty). Read the instructions on the tin (for example, you don't want a microporous flexible one designed for external wood). If you are rubbing down between coats wipe off with white spirit, not water.

It is preferable to use the same brand and system of primer/undercoat/topcoat. In most cases you won't have a problem mixing brands but it will be annoying if you do. What brand was the primer (presumably red-oxide)? the professional painters will all have their favourite (but strangely, not all the same one).

Grey is good for "killing" strong colours so they don't show, especially through white. If you are going to paint it off-white get a light-grey u/c.

 

[sifly]

Hi JohnD

I used "Rustin's red-oxide metal primer".

I'll look for a Rustin's light grey undercoat (spirit based) to put on top of it before painting the off-white topcoat.

Sound good?

 

[JohnD]

Should be OK. Rustins make a wide range of "unusual" paints in small cans, I haven't used their u/c and gloss - I expect they will be all right - if your retailer doesn't sell them, one of the big names like Crown or Dulux in matched u/c and topcoat will be OK.

"Own-Brand" paints are sometimes very good and sometimes not.

 

[sifly]

Cheers.

The topcoat is Crown, so I'll look for a light grey Crown undercoat for metal.

Thinking of next time, as there is one other fireplace to go, could I use just a spirit based undercoat and then the topcoat ontop or would I have to use the red-oxide again? The fireplace isn't rusty, but I guess it's a preventative coating.

 

[JohnD]

Use a metal primer. Cast iron is usually very shiny. It doesn't have to be red oxide, there are some grey universal primers. Don't use a "car" one or Hammerite.

 

[sifly]

Thanks for the advice. You've been a great help.

May I ask why not Hammerite? Is is for different metal or something?

Thanks again.

 

[JohnD]

Opinions differ, but it is a very hard glossy paint, does not accept other paints when redecorating. It is advertised as being good for rusty metal, but rust continues to grow under the surface

 

[sifly]

Hmmm, I see. A chap at TP said not to use Hammerite too and from your response I can see why he said that.

Oh well, I have bought primer, looking forward to a bit more painting tonight.

Thanks again.