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Fillers & Paint ?

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Malc25/04/2019 23:07:41
65 forum posts
5 photos

I am at the point of tidying up the beam engine I have been making for some time. Prior to painting there are a lot of scratches, dents etc. which need covering. I have been using “Holt’s Cataloy knifing putty” but am not too impressed with it. I didn’t really want to use an epoxy or two part filler. The imperfections are very small and I feel that a very thin brushable filler or primer would be sufficient. I would be grateful of any suggestions you fellows might have?

Paul Lousick25/04/2019 23:17:16
1370 forum posts
531 photos

Automotive spot putty is good for filling small holes and is applied with a flat metal or plastic blade. Depending on thickness, can be sanded in less than 1 hour. For larger areas, use a can of spray putty. Available from automotive paint and accessory suppliers.


Don Cox25/04/2019 23:19:35
48 forum posts

Knifing Putty is not much more than thick paint suitable for filling stone chips and the like, its hardening time is dependant on the thickness applied and much more than a sixteenth of an inch can take days to go off. P38 Isopon hardens all through in about 20 minutes and sands well, if the imperfections are that small filler primer in multiple thin coats is probably the best option.

Pete.25/04/2019 23:20:24
213 forum posts
36 photos

2K filler primer can be mixed up thick and brushed on, being that it goes off by chemical reaction, it's much better than cellulose paint, it dries nice and hard, and when sanding it's almost 'chalky' but be warned, it will leave visible brush marks where you don't sand, I have a feeling the putty you used started falling out/peeling off when you sanded it?

JasonB26/04/2019 07:05:50
17826 forum posts
1949 photos
1 articles

Spray "high build filler/primer" will do a lot of small surface inperfections. Put that on and it will show up larger problems which can be knifed and then rub it right down before using grey/red primer. Something like U-Pol's "High-5" is what I use.

More detail of how I prep and paint castings in this thread You can also see how thin the 2k body filler can be rubbed down to.

Edited By JasonB on 26/04/2019 07:09:51

Ron Laden26/04/2019 08:00:14
1865 forum posts
343 photos

Plus 1 for filler primer, as Jason says it does lose a lot of small imperfections and leaves just the larger dents and scratches, I,ve used it for years and its the first thing I apply before reaching for the filler.


Barrie Lever26/04/2019 08:25:00
462 forum posts
38 photos


I have done a fair bit of painting in my time from models through to running paint programmes for car body panels supplied to JLR.

Like most responses you have had I would go for a high build primer, Upol Reface is very good and can easily be purchased online.

Upol Reface is a polyester based product, which means it smells like normal glass fibre resin, it can be sprayed, rolled or brushed. You can spray it through something as simple as a Badger 250 airbrush (very cheap), thin with acetone to get it through whatever you spray with or like I say brush or roller.

There are a few situations where Reface does not harden properly, but I don't think you will encounter this on bare metal, the problem usualy comes on priming partially cured epoxy resin.

Reface sands superbly and if you see a slightly larger defect you can load the material in that area to take out the imperfection, bigger imperfections can be taken out with P38 type car body filler prior or after Reface, for fine defects I use Upol Easy 3 which is a very fine 2 part filler which can be sprayed over with no problems.

The model below is largly carved from Basswood and then spray primed directly with Reface and then paint coats.


BarriePulse jet control line speed model

Malc26/04/2019 14:55:05
65 forum posts
5 photos

Many thanks for the filler suggestions etc. this has certainly given me plenty of info. Now I have the basic idea I will have a shop around. Once again, thanks to all.

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