Jotun Epoxy - WARNING and question

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Plevier

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Jotun Epoxy (specifically Jotamastic 87 and wintergrade activator) comes in matching packs to give the right volume ratio when mixed, in this case 4L part A and 1L part B to make 5 L.
However if you need to make smaller batches (pot life is only 1 hour) there is a table for mixing by weight which is much easier. I was doing this on Saturday and was concerned as I could soon see I was going to have 1/4 of the can of part B left over, despite doing the weighing very carefully.
Having checked the MSDS for the specific gravity of the two materials and calculated it out, the weight sheet provided is clearly wrong. It gives you a volumetric mix of 5.5:1 instead of 4:1. The instructions say you should use scales accurate to 5 gms suggesting the mix is pretty critical.
So warning - if you are mixing Jotun stuff using the weight table, check the calculation first!
Question - having now coated the underwater hull surface with this stuff with 27% too little activator in it, what can I do? Do I need to scrape it off? I'm waiting to hear from the supplier but would be interested in independent opinions from informed forumites.
The data sheets are at http://www.smlmarinepaints.co.uk/primers/two-pack/jotamastic87_wintergrade/specification
This is a total disaster area - I'm only having to do all this thick epoxy stuff because I had the boat gritblasted and it was done far too heavily removing most of the gelcoat!
 
Troubadour said:
Jotun Epoxy (specifically Jotamastic 87 and wintergrade activator) comes in matching packs to give the right volume ratio when mixed, in this case 4L part A and 1L part B to make 5 L.
However if you need to make smaller batches (pot life is only 1 hour) there is a table for mixing by weight which is much easier. I was doing this on Saturday and was concerned as I could soon see I was going to have 1/4 of the can of part B left over, despite doing the weighing very carefully.
Having checked the MSDS for the specific gravity of the two materials and calculated it out, the weight sheet provided is clearly wrong. It gives you a volumetric mix of 5.5:1 instead of 4:1. The instructions say you should use scales accurate to 5 gms suggesting the mix is pretty critical.
So warning - if you are mixing Jotun stuff using the weight table, check the calculation first!
Question - having now coated the underwater hull surface with this stuff with 27% too little activator in it, what can I do? Do I need to scrape it off? I'm waiting to hear from the supplier but would be interested in independent opinions from informed forumites.
The data sheets are at http://www.smlmarinepaints.co.uk/primers/two-pack/jotamastic87_wintergrade/specification
This is a total disaster area - I'm only having to do all this thick epoxy stuff because I had the boat gritblasted and it was done far too heavily removing most of the gelcoat!
Click to expand...


contact Shepherd Marine
 
Yes, using the west system I had similar issues. There were precise instructions for mixing by weight but a rough aproximation if you wanded to use volume. When I calculated the exact volume mix using SGs I determined that the exact mix when using the volume method was quite a bit different.
However if your project has 'gone off' ok within a reasonable time scale then I suspect that all will be well. Was this a one coat job or have you more to apply?
 
pcatterall said:
Yes, using the west system I had similar issues. There were precise instructions for mixing by weight but a rough aproximation if you wanded to use volume. When I calculated the exact volume mix using SGs I determined that the exact mix when using the volume method was quite a bit different.
However if your project has 'gone off' ok within a reasonable time scale then I suspect that all will be well. Was this a one coat job or have you more to apply?
Click to expand...

Surely not as much difference as here though?
I do have more coats to do but of thinner stuff (Jotun Penguard HB).
 
Just heard back from Shepherd who have consulted Jotun.
Yes the figures were wrong, my calculation was right. They are doing a new sheet.
10% variation is acceptable but this is too far out to be safe.
It's got to come off.
Aargh!
 
Troubadour said:
Just heard back from Shepherd who have consulted Jotun.
Yes the figures were wrong, my calculation was right. They are doing a new sheet.
10% variation is acceptable but this is too far out to be safe.
It's got to come off.
Aargh!
Click to expand...
Who is paying?
Stu
 
What has happened to what you've put on?

Does it appear to have dried?

They've presumably been selling it for some time so how have others faired?
 
48 hrs after application the stuff is like hard toffee and when you scrape it, it stinks of unreacted component A. A mix which I did after realising the error and correcting the weights and used on the keel blade (in my garage at home) has set very hard in less time.
I have been working hard all afternoon and scraped about 1/6th of the boat at a guess. Going for a new box of carbide blades in the morning. Good thing I've just retired or this would take all summer!
Shepherd Marine have thanked me for noticing the error on this sheet that has been in circulation for about 2 years!!
They are supplying me replacement materials and have offered to supply a stripper no I mean a paint remover but reading the instructions and safety data for it I don't fancy it much (stripper might be more use to help the job along?)
Anything else? Negotiations will continue.
 
I did my bootline myself last year with a rogue Hempel product that should have been recalled from the shelves quite some time previous.

It never dried.

The chandlery got Hempel to pay for its removal & re-application (with another product) using yard labour (I wasn't going to do the job twice).

I saw the bill - mucho dinero.

Shepherd (who are a good outfit) should do make Jotun do the same.
 
Yes that was my thought but it turns out that Shepherd produced the mixing chart, it was their mistake not Jotun's.
Malcolm is always helpful and sells at very good prices. He points out it's a very small company and says he can't afford to pay for the remedial work.
On the other hand, if I hadn't just retired, I'd be having to pay someone to do it or it would take me all season.
So how far do i push him?
 
Just done son's Squib in Jotun HB & Hardtop, weighed out both lots as per the given ratios on the tin - 2 coats of each. All gone off fine :confused::confused:
 
Troubadour said:
Yes that was my thought but it turns out that Shepherd produced the mixing chart, it was their mistake not Jotun's.
Malcolm is always helpful and sells at very good prices. He points out it's a very small company and says he can't afford to pay for the remedial work.
On the other hand, if I hadn't just retired, I'd be having to pay someone to do it or it would take me all season.
So how far do i push him?
Click to expand...
He will have professional insurance (or should have to be trading!) This would pay for any mistakes on his part.
I would push him! I wouldnt like to do the job again!
Stu
 
Epoxy

Yes it has to come off because epoxy is a combining of 2 materials to make an interlocking compound.
Any short fall or mismatch in volumes of the 2 components will mean a lack of bonding to itself so lack of strength and failure to harden. I would suggest OP try methylated spirits to dissolve the unhardened epoxy.
good luck olewill
 
BAtoo said:
Just done son's Squib in Jotun HB & Hardtop, weighed out both lots as per the given ratios on the tin - 2 coats of each. All gone off fine :confused::confused:
Click to expand...

I didn't say the whole table was wrong. Those two must be OK.
Anyway it's a VOLUME ratio on the tin not weight that's a separate sheet.
 
Troubadour said:
I didn't say the whole table was wrong. Those two must be OK.
Anyway it's a VOLUME ratio on the tin not weight that's a separate sheet.
Click to expand...
Yes, we seem to have got away with it though I did find that on sanding the HB it clogged the sandpaper very easily so maybe it wasn't quite right.....
I did a quick check on the data sheets & Penguard HB is 4:1 by volume and around 5:1 by weight; Hardtop XP is 10:1 by volume & about 11:1 by weight (so about 10% different).

The addition of " BY VOLUME " on the tin would be very helpful.

Sorry to hear of your problems, I'd push him again & try & get Jotun involved too.
 
William_H said:
I would suggest OP try methylated spirits to dissolve the unhardened epoxy.
good luck olewill
Click to expand...

Interesting idea. However this isn't a thin primer, it's 80% solids applied with perceptible thickness. You scrape repeatedly and get a flake off each time. It's tough to wipe even a smear of it off with the correct thinners. I doubt anything will penetrate other than very slowly. As I applied about 3L there must be over 2L of solid to remove. Of course it's largely overhead too!
 
BAtoo said:
Yes, we seem to have got away with it though I did find that on sanding the HB it clogged the sandpaper very easily so maybe it wasn't quite right.....
I did a quick check on the data sheets & Penguard HB is 4:1 by volume and around 5:1 by weight; Hardtop XP is 10:1 by volume & about 11:1 by weight (so about 10% different).

The addition of " BY VOLUME " on the tin would be very helpful.

Sorry to hear of your problems, I'd push him again & try & get Jotun involved too.
Click to expand...

I agree it could explicitly say "by volume" but it says 4:1 and they supply 4 litres and 1 litre - bit of a hint there! Didn't you also receive the sheet with "by weight" figures on?

Actually if you did it by weight in what are supposed to be the volume proportions, you have used an excess of part B, the reverse of my situation. I don't know how the effects compare.
 
Having applied both Penguard and Hardtop over the winter, I cannot see why you even considered mixing by weight; Pint plastic containers/ mixing jugs are just about the right size to get a good mix and volume to apply before the stuff becomes to be on the point of going off. Especially in the UKs weather. The west system also uses volume, by their pumps.
It also allowed a break in routine.

Moral of the story is to do it by volume, ..........................always.
 
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