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MG Midget and Sprite Technical - Car body filler. Which brand?

Car body filler. Which brand?

Isopon is bloody expensive these days, and I haven't tried any others.

Which is the cheapest brand, and yet is still a good car body filler?

Lawrence Slater

The cheaper ones tend to absorb water and will expand. I've been using the metal loaded Isopon type filler with excellent results. I don't use a lot so I don't really factor in the cost.

Rob aka MG Moneypit

There are different filler types used for different purposes. What are you trying to accomplish?
Trevor Jessie

X2 trevor

I use what is called "Al-metal bondo" as my 1st layer, then use a good low moisture absorbing ( supplier advised ) pink bondo as the 2nd coat

But its expensive, but you get what you pay for.

Prop and the Blackhole Midget

Hi Lawrence,

Most of the bodyshops I visit seem to use Upol.
SR Smith 1

Just need it to smooth out dents and uneveness over ground down welds.

Upol is Isopon. Right?

Lawrence Slater

Evercoat Rage Ultra. Costs more, but sands very well.
Trevor Jessie

When I was building mine I read lots of articles slating talc filled body fillers like Upol due to the talc gradually hygroscopically absorbing water, that usually results in the filler swelling and popping out of the repaired area

Since I'd seen this enough times in my time I didn't want that happening to my rebuilt toy and reading about a hilariously expensive 'New Kid On The Block' metal based filler with 'No Talc' I decided on using only that in me rebuild

Then whilst I was in the build process Isopon or some such released Metallic which was the same no-talc based aluminium filled filler but reasonably priced

Wherever I have used it it has stayed put without swelling

I don't use anything else and the car has been in constant use since 2000, midget 40 at Brooklands was her first big run out

I always use a Tannin based rust eater as base when it goes over bare metal

(Where I have primed without Trustan or Fertan I HAVE had rust appear, just a thought Lawrence)
Bill sdgpM

Check this filler out. Something odd about it. Don't you think?

Brand Tetrosyl
Model USB600
Item Weight 812 g
Product Dimensions 18 x 11.8 x 10.2 cm
Batteries: Lithium ion batteries required.
Item model number USB600
Manufacturer Part Number USB600
Item Weight 810 Grams
Lawrence Slater

Got to be an extra charge for using that

Insulated gloves a minimum safety requirement no doubt

he he
Bill sdgpM

I went through the same process as Bill. For years buying the cheapest filler (talc based)and finding that it was OK, but didn't last long term. Prone to blistering and showing a swelling or cracks through the paint finish. I then started to use metal based filler instead and problem seems to be solved.

I am sure that for professional use in the controlled environment of a heated and dry bodyshop, the talc based stuff is fine. But for me, usually working outside and with the damp northern climate then talc based stuff is just a waste of money, time and effort.
Guy W

Which brand and type Guy?
Lawrence Slater

As an aside in the mid 1980s I was in a local factors getting some stuff and chatting to the assistant when another guy came in and asked about polyester resin and hardener, I can't remember how it came up, but it seems the guy didn't realise you could buy filler ready made and he was instead buying resin and hardener and mixing it himself with talc from the local chemist. The benefit was it smelt better than the ready made stuff as the talc powder came perfumed. Personally I've never had any issues with talc based filler but have always tried to minimise its use and haven't tried the metal based fillers but when I come to need some next may give them a try.
David Billington

I'm not sure why the "talc" based fillers are failing. If they are absorbing moisture through your paint then you are using the wrong type paint or your panel is not prepped properly.
Trevor Jessie

I think in our damp climate the moisture is absorbed by the talc based fillers before they are protected by paint.
Guy W

Guy. Which brand do you favour?
Lawrence Slater

Sorry Lawrence, I missed your earlier request. I don't read your messages as avidly as I once did.

Its a while since I bought any, the last one being Plastic Padding "Chemical Metal" IIRC. Its not a recommendation as such I just buy whichever is readily available, so long as it is a metal based variety.
Guy W

The very best filler I have ever used, I found when repairing my Elan's fibreglass body. It is International Watertite, a 2-part epoxy filler. It is extremely smooth and easy to apply and is (as the name implies) completely impervious to water. I love it.
Mike Howlett

Thanks Mike.

"I don't read your messages as avidly as I once did." That honestly made me laugh out loud Guy. :). And surprised me. I hadn't realised you'd ever paid much attention to what I've written. ;).

OK, I'll have a look at both of those.

Lawrence Slater

Don't flatter yourself Lawrence! I have my browser set to the BBS "Last posts" view and there was a time when I would avidly read all messages under the 3 Midget and Sprite boards, irrespective of topic or author. Latterly I have been more selective, ignoring posts under certain thread headings, and very occasionally selectively skipping all posts from particular individuals.
Guy W

I use this for bits that require a bit more work

Dave Pratt

And this for smaller bits

Dave Pratt

As a body filler I like West System epoxy. Various grades of glass fillers/thickeners available. Good information on the 'Net about this.

I've mostly used it for GRP boat hull repairs, but have used it successfully on minor car body filling too. It's super-strong and completely impervious to water.

I think it's "reassuringly expensive" but I don't know for sure. Somebody else pays for it!

Isopon P40 I've found much better than P38 as it is also impervious to water and reinforced with chopped glass, but it's harder to get a fair surface and needs a smooth stopper coat as a finish. P38 sands smoother, but takes up moisture and is not as structurally tough.

I hadn't heard about International Watertite but I'll definitely look at that next time. Thanks Mike - good tip.

For small imperfections I'd be tempted to look again at lead loading. I haven't done it for donkey's years, but I was reminded about it by a recent thread. Wouldn't mind having another go, it's not too hard as I remember for small areas.

Also thanks Dave for your posts. I hadn't heard of either.

"Latterly I have been more selective, ignoring posts under certain thread headings, and very occasionally selectively skipping all posts from particular individuals"

Sound approach to this bbs Guy, one I will follow from now on.
Pete Ottewell

I wasn't Guy. Exactly the opposite in fact.

That choice has always been there Pete. Nobody has to read or respond to anything. If there's a compulsion, it's in your own head.

Thanks Rod, Dave.

Lawrence Slater

Psychologists as well Lawrence you really are a clever guy. That must be how you diagnosed me as a nutter.
Pete Ottewell


UPol is a brand, not a grade. They sell rough and smooth (finishing) grade fillers, akin to Isopon P38 and P40, see:
Body and finishing fillers in:

Check out your local motor factors/car paint suppliers - UPol seems widely available these days.

M Wood

U-Pol do seem to be the trade-preferred brand around here. They also list a version, U-Pol D, with aluminium filler added.

Whether that is any different from their other fillers regarding the water absorbency issue I wouldn't know. I suspect for most applications, and certainly all professional use in proper bodyshops, water absorbency just isn't an issue anyway. Its only a problem if you work outside in damp conditions, with possible extended delays between applying the filler and adding the final waterproof paint finish.
Guy W

I've saved this thread to my computer for future reference. Cheers chaps.

He Pete. I didn't need shrink training, it just obvious. LOL. ;). Anyway, what happened to following Guy's approach?
Lawrence Slater

I never said that i was going to ignore your posts Lawrence, you opinions mean so mush to me. If you really knew me you would know how wrong you are about me, but then again your never wrong are you?
Pete Ottewell

"Sound approach to this bbs Guy, one I will follow from now on."

I think it was reasonable, given the context of Guy's comment, that you were going to ignore me from now on.

Anyway, likewise Pete, except that it's true. I'm never wrong. ;).
Lawrence Slater

As Guy already said Lawrence don't flatter yourself.
Pete Ottewell

I'm not Pete. It's true, I'm never wrong. lol.
Lawrence Slater

This thread was discussed between 10/10/2015 and 18/10/2015

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