Jotamastic 87 - brush application without thinners?

[ashy90]

In the process of protecting the underside of my MG ZS in the scabby areas.

I’ve got the 4L tin of Jotamastic 87 I’m going to apply by brush / roller once down to bare metal, which came with 0.7l of thinners. Basic question, but this is new to me - if I am applying by brush/roller, am I right in thinking I don’t need to use the thinners?

Thanks all

 

[qwakers]

correct

 

[badabec]

I bought 5 litres of thinners and 10 litres of Jotun, brushed and rollered on my DS. I still have 5 litres of thinners in an unopened can.

Make sure your rollers are suitable for epoxy otherwise they do like to swell and fall apart.

 

[barracuda816]

I think it's dependant on the finish and environment you are working in. I generally found a splash of thinners helped to flow out the brush marks. But if you are not conserned about brush marks, then no thinner needed. I would recommend a roller for as much as you can, and I always put subsequent coats on at 90degrees to the previous. Not sure if it really helps or not but I feel like it gives a better uniform coating.

 

[ashy90]

Ok thanks for confirming.

What if I were to use Bilt Hamber Epoxy Mastic instead - I am assuming as it is supplied with a hardener and not thinner, then the hardener is required?
I’ve got a 800ml tin which came with 200ml of hardener which will probably be enough for the area I’m treating.
The only instruction on the tin is to mix 4 to 1 and apply by brush or roller.

 

[Slowcoach]

Are you certain you got 0.7lts of thinners and not hardener. The hardener is definitely important.
SML have a good info on downloads for jotun. This is primer/ hardener ratio by volume for aluminium.

 

[ashy90]

Are you certain you got 0.7lts of thinners and not hardener. The hardener is definitely important.
SML have a good info on downloads for jotun. This is primer/ hardener ratio by volume for aluminium.
View attachment 513512

You are absolutely correct! I’ve just opened the box up and it is indeed 0.7l of hardener. So this must be used regardless of how the Mastic is applied?

 

[DanZac]

You are absolutely correct! I’ve just opened the box up and it is indeed 0.7l of hardener. So this must be used regardless of how the Mastic is applied?

Yes, or it'll never cure and you'll just have a sticky mess to deal with.

 

[Turbo]

See if you can find the mixing ratios by weight.
It is a lot easier mixing by weight. Set your mixing pot on a set of electronic scales, zero the scale, add your paint, note the weight then add the correct amount of hardener.

Its easier to watch the digital weight display than try to see the scale on a mixing cup and a lot more accurate.

Particularly important if you are mixing a small quantity to get the ratios correct.

 

[Turbo]

As regards the thinners, it will flow a lot better with a drop of thinners added and will go into nooks and crannies better, particularly with a roller.

 

[ashy90]

Ok I used Built Hamber epoxy mastic in the end - mixed with the hardener and brushed on.

I now need to apply a second coat, should I abrase with some 120 grit sand paper and scouring pads before applying the second coat? It's been a week since I applied the first coat so it must be fully cured now.

 

[badabec]

Nothing in the rather sparse data sheet and no technical data sheet.