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MG Midget and Sprite Technical - Brushing or Rolling 2 pack paint

Thought I would make this a new thread as it came up in the "GN15 Leaf Green paint" thread.

I got some 2 pack (BLVC16 aka Blaze) and some activator from the local paint factors. They were a bit reluctant as they were not sure whether it was dangerous being brush painted but they did sell it to me in the end.

Things I have found out today.

1/ It is quite thin to brush so you are going to need 2 coats.
2/ As it is thin don't put as much activator in it to keep it as thick as possible. This has the advantage that it will take longer to go off.
3/ It is by far the smelliest paint I have experienced. A mask is advisable as well as good ventilation.
4/ Whatever thinning agent is used in the base paint it flashes off very quickly and from then until it goes off it will drag unless the brush is well loaded.
5/ My shell had already been stone chipped so was a very bumpy surface to paint. I needed a short haired brush and stippled it on. This had the advantage that I could put it on quite thick at panel joints.
6/ Paint the hard to reach parts first. I didn't and it is quite difficult getting right inside the transmission tunnel when other bits have been painted.

The information sheet I got with the paint said 3 parts paint, 1 part activator then 20% thinners. This is for spraying and the pot life is quoted as 6 to 8 hours. I did the 3 + 1 paint to activator ratio and it was going hard after about an hour. Luckily, I got to the end of the small amount I had mixed.
Next time I will reduce the activator ratio to 1/2 the recommended.

I only put one coat on. It's very shinny. 2 hours after starting it felt very hard. Not tacky at all.

I'm not certain how a second coat will go over a fully set first coat. I will find out tomorrow.

MG Moneypit

Useful assessment Rob. Good luck with coat 2.
Like many of these jobs, in my experience one just about masters the hang of it when you get to the finish! ;-)

I guess my question is ... WHY?

YOU can get those cheap new purple hvlp gravity paint guns for around $20 from ebay and your power mart stores here in the states harbor fraight carrys them... there basically a one to 2 time gun ... then pitch them in the trash... and they do a decent job

A compressor is dirt cheap to buy now or you can barrow one... 1000s of them around...a lot faster and a much nicer finish job


1 Paper

Cheers Rob, useful info. My guess is that the second coat will go on fine. As its a chemical reaction that has cured it, I don't think another coat will touch it
John Payne

Prop. The problem with spraying 2 pack is the mist contains iso-cyanates. If you breath them in it's a quick way to your blood stream. Cyanide in your blood is a no-no, but brushing avoids breathing in the mist so it's much safer.

Of course, you should wear gloves even if you brush it on and whatever you do - don't drink the activator!

MG Moneypit

Well yeah.... if your creatimg a mist cloud you should always but on a mask regardless of the chemical make up.... you think smoking is bad for the lungs try a table spoon of any kind of paint into your lungs is gokng to set you back a few days... no argument there

As to the chemical make up of the paint... time vs ventialation is key, you doing a whole car your paint sounds fumy to say the least but your going to be exposed to a lower volume over a much longer period of time, allowing those chimicals to build up in heavier consentrations much slower

Its better to introduce ventilation get in and get out fast and id use a resperiator with filters designed for the chemical make up of the paint your using

Considering its a hole car id build a 1x1 wooden cage staple some 3mil clear platic over it with a box fan at one end and a home AC hvac filter at the other end a hole in the top for dprayer hose and use a resperator i discribed above and get in get it done and get out yes even wearing protective clothing

This way your exposure is minimal, no outside the wrea enviormential issues and its all contained and no dust or foreighn particals in your newly painted car and no brush /roller marks

Just because you can smell it from rolling it, dosent mean your avoiding the chemical intake... your still doing it over a much longer time. Which is far worse then instsnt hit

Think how to boil a live frog ... samething your doing by rolling it... by the time your finally feeling the effects of chemicwls being absobed into your lungs ... your screwed

Also remeber that chems volitility sometimes expands with temp and humidity

If its being forced out of a gun its expansion eill be almost instant but if a chemical is in a coffee cup its expansion can take considerably longer so it could litterly start its expansion once inside your lungs even tho it appeared invisable to you when you inhaled it.

Tjat said... you wont die from anything isaid above... its an event you will suffer thur mayne 5 times in a life time, now if you do it every day... oh yeah your dead with in a few years

Sorry for both apperance, durability and safety... i disagree with rollimg and brushing as your doing... but if we all agreed ... then that would suck...haha
1 Paper

I painted my Elan with 2-pack International Yacht paint using a brush. My experience was similar to yours. It had a terrific gloss but brush marks were obvious, so I spent ages smoothing and polishing with 1500 grit wet and dry. It turned out well but was a lot of work.

Mike Howlett

Mike, turned out well?! That is some understatement!!
John Payne


My neighbour used 2 pack International yacht paint when he brush painted his miniature steam locomotive and got an excellent finish with virtually no brush marks, at least on the 2nd attempt, the first can had some sort of contaminant in it that left bits in the surface, the supplier gave him a new can FOC and that was fine. IIRC the instruction were to brush or roller the paint but not spray due to the hazard. In the end he went over the paint with fine wet and dry like your 1500 or similar to remove the gloss and give it a more appropriate finish for a working loco.
David Billington

I wouldn't spray 2k paint without an air fed mask, ever. I know some people do.
I'm not that keen on breathing on the solvent toluene either so I generally
use the air fed mask rather than a filter mask when mixing and cleaning up as well.
P Simpson

Couldn't agree more----
Rob--Playing games with your health here
You wrote----
"3/ It is by far the smelliest paint I have experienced. A mask is advisable as well as good ventilation."
Bad news is---if you can smell it, It's going in and it's not coming back out--
You need a mask with an air supply----minimum
William Revit

Rob isn't spraying he's brushing. Having read the HSE recommendations I'd be happy to brush paint it, I'd probably avoid rollering though and I'd wear a decent mask to get rid of the fumes if nor well ventilated.

Here's the recommendations plus some other stuff I've found:

John Payne

Here's the HSE sheet:
John Payne

I have only resprayed a couple of cars and in both cases I used cellulose and achieved OK results. both times I used a new 3m face mask for each car for primer and gloss and I couldn't smell the paint whilst using it.
With cellulose, you can polish a finish from it so providing you have the right tools and time, some pretty good results are achievable by most of us.

From what I understand of Two Pack, its not only dangerous from what you will inevitably breath in, but the iso-cyanates can/are absorbed through any open cuts, grazes and also through your eyes. . . which would explain and endorse the boiler suit, full face, air fed mask get up that you see the pro's use.
Whilst I understand that excellent results can be achieved by brushing, and roller painting, (proved by the Elan picture) there is a reason why a spray gun is used, it clearly has both performance, time and cost advantages over the brush approach, but I do follow that for a home user time considerations are not always so relevant.
P Bentley

I should point out I have absolutely no intention of spraying 2 pack. I'm only using a brush to apply 2 pack to the underneath of the Sprite and any other hard to get at areas you wouldn't expect a professional bodywork sprayer to reach.

I intend to get the top of the car, including engine bay, inside boot area and passenger compartment of the car, as well as the exterior, sprayed by a professional.

MG Moneypit

Yes I understand you're brushing, it was the other comment about spraying I was referring to, which seemed a little vague about the type of mask. I've just never been confident that my filtered mask keeps everything out unlike the airfed.
I've brushed 2 pack on things without trouble, I mix it as standard. I got good results for small repairs if sanded and polished before it is rock hard.

Your approach sounds like pretty sensible use of time and resources to me.
P Simpson

I think something has not been made clear about the non-air supplied painting masks.

The non-air-supplied masks are designed to filter out particulate (like overspray) and they are made to capture certain solvents.

The medium in the mask determines what solvents they will capture, but generally they are designed to capture volatile organic compounds (VOCs) such as toluene, xylene, mineral spirits, etc. I think that iso-cyanates are inorganic chemicals.

I don't know if it is still true today, but as of a few years ago, there was no filter medium that would capture iso-cyanates. Thus the requirement for an air-supplied respirator.

If brushing the iso-cyanate coatings is safe, that means that the iso-cyanates are not volatile. I know they are primarily supposed to react in the coating (unlike a solvent carrier that is supposed to evaporate) but I don't know if it is volatile to some degree. Rob may have investigated this, but I would check that myself if I intended to brush it without air supply.

C R Huff

You're right about negative pressure masks they're really designed to filter out dusts, some though have carbon filters that will adsorb some organic solvents as the air passes.

Isocyanate is actually an organic chemical (it's not a solvent) and is the active ingredient in superglue. As You say, when you use 2 pack paint the isocyanate is acting as a very thin layer of glue holding all the paint particles together (that's the difference between drying as the solvents evaporate and setting as the glue binds), to me that's why 2 pack paint is hard and traditional paint feels slightly soft

The thing with isocyanate though is that it's really toxic, compared to a solvent like toluene, looking at the safety data sheets for 'tlv'- toluene is 300 ppm, isocyanate is 5ppb (m = million, b=billion) translating, isocyanate is 60,000 times more toxic than toluene. Isocyanate was the chemical at Bhopal that killed thousands

A negative pressure mask doesn't protect you enough - those things work on creating a negative pressure that pulls the air in past the carbon filter. The trouble is that unless you have a really good fit, air just leaks in without passing the carbon

the HSE has a useful data sheet at - sorry don't know how to make that a link so you'll need to cut and paste

I'm not being a health and safety nazi, you should all make your own decisions but be informed when you do it - don't assume negative pressure masks will protect you enough, for occasional use and not spraying (which minimises fumes) you're minimising exposure (I'd probably do that) but don't assume the mask is doing you any good


Clickable link -
Dave O'Neill 2

Tim, thats interesting about the active ingredient in superglue as sometimes hospitals use a type of it to hold cuts closed rather than stitches. If it contains that I would not have thought that was a good idea. Of course it may not be exactly the same stuff but would be interesting to know.

T Mason

Cheers Tim, some good info there. The HSE's recommendation is pretty clear, don't spray with 2k Isocyonate without the right gear but brush application is ok (still with some precautions).
A lot of the substances I use at work are similar, the Dinitrol type stuff we use for example is ok for brushing but deadly when sprayed.

What I haven't looked into is whether spraying non isocyonate 2k without an air fed mask is ok. I've heard people say it is but personally I don't think I'll be risking it.
John Payne

Doesn't seem right inhaling something that then subsequently sets in your alveoli as the hardener cures it, even if the hardener itself isn't a toxic isocyanate!

Isocyanate can give a hypersensitivity reaction and specially in persons who are genetical prone to those reactions. If there is astma eczema etc. in the family. The exposure true the skin is the most sure way to start the hypersensitivity reaction. It takes 9-10 days from first contact to allergy. If the allergy already exists it takes some seconds after exposure to get the allergic reaction, witch is seldom lethal. There is no correlation with the dose. A few molecules are enough. There is a strong correlation with the frequency that you are exposed.
If you roll or brush it always wear gloves. Even a good filter mask will not help you to prevent an allergy against isocyanate. An over pressure mask and suit will help for some time. Sooner or later you will make a fault and come in contact with the stuff. So a professional should never spray two pack unless he or she accepts the risk and works for him or herself. A sensible boss in the UK or US will never accept working with 2 pack.

(I do have two pack on my car, it it lovely, very strong, looks marvelous, is long lasting and easy to repair. After 20 years the original paint witch I
save in a metal container at low temperature is still good. And yes I am a proven allergic...)

Flip Brühl

It definitely sounds dodgy stuff Flip!

If it really is that bad then why do people use it? You say that professionals shouldn't accept using it - so what do they use?! I was under the impression that it was the only thing they did use.

Certainly the painters I work with have been spraying, brushing and rolling 2k isocyonate type paints all their lives - and some of the stories they tell make you think they should be dead by now! They are always telling us how dodgy it is though.

By the way apparently even rubbing down paints with isocyonate content is dodgy - so use a mask, good ventilation and perhaps dampen things down.

John Payne

Yes, I think the ISO-cyonate is a catalyst which causes the chemical reaction but doesn't change it's state. Once it hardens it is still there though locked in. If you sand it dry make sure you have a good mask and I suppose don't allow the dust to touch your skin especially if you are sweaty which you will be if rubbing down. Wet sanding should be OK as long as you wear suitable gloves.


MG Moneypit

This is getting worse and worse. I was just about to do a paint repair on my modern car which would involve rubbing down 2 pack (but not painting with it). I always do that bare handed to get a feel for the surface. Now I'm concerned about it.
W Bretherton

I found this which might be useful and probably means my conjecture was wrong, after the paint is fully cured.


"Sanding down:
When isocyanate paints are fully cured, if they have been applied for more than 24 hours at room temperature or heated for one hour at 70°C, and are sanded down, the dust produced will not present an isocyanate hazard. This is because fully cured paints contain no free isocyanates. In such instances a dust mask should be worn to provide protection from the general nuisance dust present. Where new paint that may not be fully cured is sanded down, the dust will contain free isocyanates.

A particulate respirator fitted with Class H filters should be worn. Where practical, the use of wet sanding methods is recommended as a means of reducing the amount of dust generated."

MG Moneypit

So far I have brush applied almost a whole tin (1 ltr) of 2K to the bottom of the Sprite. See image.

Two coats have been applied to the whole of the bottom, one to the inside of the transmission tunnel, chassis members, steering rack support and radiator support uprights. I have applied 3 coats to one of the front wheel arches and I probably have enough left to put 3 coats in total to the other 3 wheel arches.

I'm going to get another tin to complete 2 coats where there is presently 1 coat and will probably continue with 2 coats on the foot well sides and in the battery compartment area both of which will be well hidden by other things when built up.

It is applied over stone chip. The stone chip was applied over etch primer by the previous owner.

There are no brush marks that I can see. I don't think it is my brush painting skills, more likely disguised by the dimple effect you get with stone chip.

I used 1/2 the quantity of hardener recommended for spraying. It didn't appear to go off at all in the 1 hour it usually takes to use the small quantities I mixed. It goes tacky due to solvent evaporation when applied, is dry about an hour later and full hardness overnight. It has a good shine straight from the brush.


MG Moneypit

It looks marvelous!
Flip Brühl

Yes Rob, that is looking good!
What sort of quantity did you find convenient to mix up at one time?
What sort of roller brush were you using?

For others considering this, here is the text of the H&S information provided by the British Coatings Federation:


a) Brush and roller application
Application by brush or roller does not normally generate paint mist containing isocyanates and therefore the risk of asthma is negligible. Aggressive rollering might generate mist and if this is likely RPE should be worn. Gloves should be worn and normal personal protective equipment could be required especially if solvents are present.

b) Spray application
Application by spray is the main cause of inhalation exposure to isocyanates. etc. etc. (continues with extensive health warnings)


1. Brush and Roller application

Provide health and safety training – inform workers that they are working with isocyanates and that these can cause asthma and dermatitis
Provide disposable overalls – discard at end of day
Provide chemically resistant gloves – single use gloves preferred, throw away every time they are taken off
Ensure adequate ventilation Air-fed respiratory equipment is not normally required, however eye protection may be required Avoid application that might cause a mist
Decontaminate brushes and rollers before disposal as hazardous waste

The info sheet says for spraying 3 parts paint, 1 part activator then 20% thinners but that is obviously too thin for brush applications.

I went with 3 parts paint + 1/2 (half) part activator. This gives plenty of time before it goes off. I mixed about an hours worth of brush application.

I never got around to using a roller but I should have used one for inside the transmission tunnel. It was a bit awkward with a brush. I had to cut the handle in half. Start at the point where your arm is all the way inside the tunnel and paint toward you. I maybe could have used a right angled brush for painting behind radiators but I didn't want to get changed, drive to B&Q etc. Or a mini roller with a long handle also for painting behind radiators might have been better.

As I didn't use a roller I can only say the foam type is probably better than the hairy type.

I re-used the paint brush by washing immediately in thinners and never had problems with it going off on the brush.

I did 2 coats over everything underneath, and an extra coat under the wheel arches. I think a brush for all the awkward bits and persuading the paint into joints follwed by roller on flat bits would have speeded it up.


MG Moneypit

Thanks Rob. I got the thinning ratio earlier - at least approximately!
The question was about how much to mix up at one go:
"I mixed about an hours worth of brush application."
I am guessing maybe about 350ml?

Hard to say. I found a plastic top from a K&N airfilter oil aerosol and used 3 of paint and half of activator.
This top was a lot smaller than a rattle can aerosol top.

I will measure it when I get home.

MG Moneypit

Not bad at all, well done

Just a point..i never use foam rollars, the differ from manufature to manufature...and they tend to fall apart little by little in small pieces there is no consistancy for when how often or what conditions the foam breaks down

For a nice smooth finish using a 4inch roller i like sort nap valor cover... the ones i use are purple ...the secret is to pre soak them 10 to 20 minutes in the paint you going to be usingin order for the cover fibers to fully absorb the paint, and thwt will give a nicer finish

But aviod the foam... there is little consistancy performance wise and tend to break down inside of an hour even under normal laytex piant conditions...also because of there bulbous shape at both ends, its easier to get piant streaks and runners where as the valor ond similar material roller covers are squared off and not bulbous at the ends the paint dosnt get pushed/falls out as easily

You can also tape a paint mixing stick to your brush to get into those deeper wierd recese, but yeah, ive always modifed my brush handles to fit the job in odd situations... also you can cut the bristels back to form the shape you need.

1 Paper

Useful tips there Prop.
At one time in the UK you could buy velour-type paint pad things in various sizes. They seemed to work quite well but I don't think I have seen them for years now.

As an alternative, I see that Jawel Paints do a 2K Acrylic paint that uses a non-Isocyanate hardener. The claim is "all the benefits of 2K without the health concerns associated with isocyanates"

Sounds interesting, except reading the detail, it says it converts a 2K to an air drying product so I assume that it then has the downside of risking picking up dust etc before it dries. So not quite "all the benefits" as claimed!


If that paint is converted to an air dry paint and its noally a chemical process for drying and curing then your goijg to get a slow drying paint that may never actually cure ... dry to touch yes but cure maybe not... that means the paint will never really shine as the molecules can never be realy compressed or shaved off smooth and it will be easy to scratch and hard to keep clean and would be easier to stain

So unless its just a samll area, id. Avoid that paint also

In my opinion anything that used to cure because of a chemical process and been made to cure thur enviromential conditions for the purpose of convinance is just going to tuen into a long day.

That said you can alt. The enviorment to make the chemical process more efficant by removing humidity and adding heat even ultraviolet light can have an effect on chemica curing processes

1 Paper

The company selling this non-isocyanate hardener is a well respected firm. If they call the product a hardener, then it will be doing just that, it isn't just an air drying process that as you rightly say might never fully cure. But it does say that it takes longer to activate than a normal isocyanate, which is why I would think it might be more prone to dust contamination as it cures.

Rob, back on your brush application of an Isocyanate. I understand that you increased the curing time by reducing the hardener ratio. Were you using a "slow" grade activator or a "fast" grade? According to the data sheets at the normal ratio and when spraying, a slow grade would take 30 to 45 mins whilst a fast would take 15 to 30 minutes.

The activator was a fast activator.

Paint pads are available at B&Q. I bought a set and after a few minutes trial I binned them. Not sure why but I couldn't get the hang of them and went back to brushes (this is for painting a wall with ordinary emulsion).

MG Moneypit

Guy ... i agree with you, the long a paint stays wet to touxh the better the chance of containaments

On the other hand... the longer the paint stays wet to touch, rhe better the finish cuz it has more time to flow out and level its self.... so its yen/yang balancing act.

Augh... are you referancing rhose sq pads with the little rollers on the side... if so, you made the right choice to bin those, and im amazed how long those have been around. Maybe i lack experiance using them

1 Paper

Well, encouraged by Rob's efforts with his Blaze paint, I have just given the underside of the Frog its first coat of Iris Blue (Not Leaf Green after much indecision!), using brush-applied 2K, as Rob did.

I used a slightly different formulation after talking to the paint suppliers who were very helpful(Jawel). I used the recommended 1 part hardener to 2 parts paint + 10% thinners as they said that if I reduced the hardener ratio, as Rob did, the paint might not fully cure. I wasn't sure about that as Rob didn't appear to have any problems dropping to half that concentration with a "Fast" hardener. But they said to use both "Slow" hardener and thinners so I went along with that.

The paint went on well, brushing out quickly and easily and didn't thicken on the brush as time went on. I used a face mask certified for both organic and inorganic fumes, plus goggles, full paper disposable suit and nitrile gloves taped at cuffs. This is a higher level of PPE than HSE recommend for brush painting 2K and I couldn't smell the paint at all until I took the mask off when I had finished. Even so, its not a pleasant job - and I have another coat to do yet!


Wow - looks great, well done. How long does it take to cure and do you have to wait for complete curing before you can recoat?

Guessing the slow hardener is to allow time for the thinner to evaporate, is that right?

Given that these products are design primarily for spraying, one would normally use a Fast or a Standard hardener, and a professional paint sprayer would use a Fast thinner to get the paint to flash off quickly allowing the next coat to go on more or less as a continual process. I was advised to use a slow hardener to allow time for brush painting, without it going claggy (technical term) on the brush. It certainly didn't do that and yet now, about an hour and a half since I finished, the paint is dry without a hint of tackiness.

I guess I could probably apply a second coat now, but I just don't fancy going through it all again today.

Looks great Guy. If mine ends up anything like that I'll be well happy. Thanks for the tips (from you and Rob), should help loads for other people in the future.

It's a big decision on the paint colour and I can guess the sort of indecision you've had! Iris is a great colour and always looks good on a Frogeye. The greens are difficult I think, sometimes you see a Almond or BRG car and it looks fantastic, then you see another that's not as good. I think the paint has to be the exact shade with greens or it can look odd.

John Payne

About the green colours - I speculated on an earlier discussion of my choosing a colour that greens are difficult because as a species we have evolved in a wooded or at least vegetated environment of such a diversity of greens. And for the human eye the green spectrums are pretty well dead centre in the range we can see. I think that this makes us more sensitive to variations in colour between shades of green and some just look wrong!

Anyway, my decision is made now. BU12, Iris Blue. Or Irish Blue as I found it listed on one American chart of BMC colours!

What you say about greens seems entirely reasonable. And as John remarks green is tricky with probably more shades of preference among different people. One of my Mercedes Benzes was the exact colour of a manzanilla olive, which I liked a lot but SWMBO didn't. She called it khaki.
An old fellow I knew long ago who raced in the 40s and 50s told me that BRG was originally a flat and fairly ugly colour used by (I think) Lister and Connaught race cars and what we generally call BRG now was a Jaguar shade called Holly Leaf. Very popular with the Morganistas.

I'm not generally a fan of blue, but the colour in your picture reminds me strongly of the French Blue that Bugatti raced in. I like it. Maybe just because that was the colour of my dad's Tipo 35b. All in the eye of the beholder eh!

Personally I have a bit of a thing about yellow, but it's not everyone's cup of Rosie.

Thought you would like the combination of orange and dark blue?

My 1500 was yellow, as many were


Nice! Mine too, but I like the black sills.

The Signal Orange/Oxford Blue combo looks ugly to me, but I know a few people who have been happy to see it lol!


I thought yours might be the same colour! That's why I posted that picture of mine, sold some 16 years ago. I see it is still currently taxed and presumably threfore in use.


That is quite a milestone after all the fabricating/welding. Looks great and I like the color choice.

C R Huff

This thread was discussed between 17/06/2017 and 10/07/2017

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