Scalefour Forum

A couple of days ago I lightly sprayed two pannier body shells I've been modifying with Holts grey primer, the cellulose type. I only applied a light coating to show up any imperfections which needed further finishing, and having shaken the can for at least the prescribed 2 minutes, leaving them to dry and coming back to them today, the primer is still slightly tacky and shiny. Could this be due to the warm weather? Annoyingly, any further rubbing down/scraping has now stuck to the primer so its back to the brake fluid bath!

Steve

I primed and painted a set of wheels yesterday and now completely dry. Did them outside in about 18 degrees so it’s not the weather. Both Halfords enamel.

Could it be that you have sprayed a plastic body with cellulose and it has reacted?

Thankfully the grey primer came off easily with brake fluid. Having got the locos clean again and rectified minor blemishes etc. I am wondering now - is priming really necessary on plastic models?

I'm wondering because when I stripped the original paint on the pair of Bachmann panniers, the base plastic is black, apart from the few whitemetal fittings I have replaced, the entire body is matt black. Given pre 1928 GWR green is very dark, would it be appropriate to paint direct?

Steve

Yes, absolutely on plastic. We use "primer" to mean many things such as "surface preparer", "undercoat", "reveal coat" or "colour density coat". On metal I've always used an etching primer to prepare the surface, but on plastic only a reveal coat and possibly colour density coat but there's no reason why those last two need to say "primer" on the tin - you just need a suitable Humbrol matt.

Similarly, you might need two different paints that "prime" the surface in some way. So on metal, as said, I use the etch primer, but that is pale grey and some colours might need a coat of another colour over that for colour-density purposes - white base for yellow, red oxide for black. As before, that second coat can just be Humbrol matt. So two "primers" in that case.

Enigma wrote:Could it be that you have sprayed a plastic body with cellulose and it has reacted?

I agree with Paul. Cellulose should not be put on plastic.

Reminds me of Floquil paints (remember them), there was a barrier paint to be put on before using them.

Thank you gents for useful responses, I've always used grey cellulose on metal models so I suppose it was force of habit that made me use it on these plastic bodies. Hopefully the pre1928 GWR green (Precision) will take happily on the already matt black plastic!

You live and learn in this game

Steve

Tim V wrote:

Enigma wrote:Could it be that you have sprayed a plastic body with cellulose and it has reacted?

I agree with Paul. Cellulose should not be put on plastic.

Reminds me of Floquil paints (remember them), there was a barrier paint to be put on before using them.

I remember Floquil paints well.

I still have two jars of them - one of copper and one of brass paint. As metallics, they have the finest grained pigment in them that I've seen in any paint. I've only ever used them on whitemetal, so the need for (or problems from the lack of) barrier paint has never arisen.

The problem of washing the residue of paint out of the brush afterwards is a different issue though!

Cheers
Paul