Using Jotamastic

[system 4-50]

I can't find any record of my having posted these notes on using Jotamastic 2-part epoxy blacking on my boat and they might be useful to some so here they are:

Jotamastic 87 Method & Notes

01. None of the following is guaranteed. Check everything with the official documentation. This information is provided in good faith and is as accurate as I can make it. It is my notes to myself, which might be of interest to others doing this for the first time.

02. I obtained the paint, Jotamastic 87 (J87) from SML Paints & Coatings - fast delivery, excellent telephone service, fairly good website - strongly recommended. Tel 01258 862132 W: www.smlpaintsandcoatings.co.uk

Materials needed (per 4.6L paint where applicable)

01. Hard hat, Eye mask, Fumes mask - this paint is evil stuff and is particularly harmful to eyes.

02. 100 rubber gloves nitrile from SML - very good

03. Pot opener from SML - very good!

04. Pot A & Pot B Jotamastic 87(standard grade). SML provide both automatically.

05. Tissues

06. Waste sack

07. Knife to open pot A plastic bag

08. Stirrers - 1 big & 6 small (available from SML but I used bits of dowelling)

09. Scales from SML (very good) - mixing is done by weight

10. Mixing pots from SML - 1L x 6

11. Writing pad & 2 pencils- for doing the 11% calculation

12. Hammer

13. Brushes - 3” - x 6 - use-once-and-throw-away brushes from Toolstation at 63p each

14. Clock - or any other easy to see timepiece

Method Used

01. Remove pot A from plastic bag & save the bag for later storage.

02. Open lid with opener - easy

03. Stir pot A - takes about 15 mins, do about twice a day (stirring small pot B not attempted). This is crucial as the contents separate markedly.

04. Do not use tare (including mixpot weight in zero) as the scales reset themselves after 120 secs and you could get results that lose the weight of the pot.

05. Switch scales on & wait for zero with nothing on it

06. Weigh empty mixpot usually 94g

07. Remove mixpot from scales

08. Pour A into mixpot until about 2/3 full max or less as required

09. Switch scales on & wait for zero with nothing on it

10. Weigh mixpot

11. Write down mixpot weight - this is the TOTAL POT WEIGHT

12. Remove mixpot from scales

13. Replace lid on pot A - protect hammer with tissue and wipe pot A clean as best possible

14. Deduct mixpot weight to obtain paint A weight

15. Calculate 11% of paint A weight

16. ADD the 11% of paint A weight to the TOTAL POT WEIGHT to give the FINAL POT WEIGHT

17. Open pot B

18. Switch scales on & wait for zero with nothing on it

19. Put the mixpot on scales

20. Pour pot B into the mixpot slowly as the adding amount is small until the FINAL POT WEIGHT is shown on the scales.

21. Steady is best as it is hard to get small globules out. It is possible to get it exact, it is not too difficult.

22. Put pot B down on 2 layers of tissue as B is sticky & messy and much harder to manipulate without mess than A.

23. Remove mixpot from scales

24. Note the time - your pot live time starts now.

25. Replace the lid on pot B

26. Wipe pot B roughly as it is not possible to get it fully clean. Don’t get tissue stuck in it. Don’t hit the lid too hard, the tin crushes.

27. Use a small stirrer to mix the contents of the mixpot for at least 5 mins

28. Leave until about 10 (about 5 more) mins from the noted mix time for the mixture to acquire its working consistency. Before this it may be too thin and hard to apply at the correct thickness. This 10 mins is known as the “induction time”.

29. Use a 3” brush to apply the paint to the surface.

30. Start low down and work up to avoid getting it on your head.

31. Brush both up & down & right & left as it visibly improves the thoroughness of the application.

32. You have an absolute maximum of 2 hours (and sometimes less) to apply the paint before it goes off from the start-of-mixing time.

33. It gets markedly thicker after about 1 hour and then is slower to apply.

34. Hot weather seems to make it go off slightly faster.

35. It is touch dry in about 7 hours.

36. It is overcoatable in about 10 hours minimum. It can be overcoated later for some time, but (I think, I have not checked) it is best done within 48 hours. (if you leave it too long you may have to sand it again, I don't know as I didn't take any holidays.)

37. It is fully cured and ready for service after 7days.

General notes

01. The paint can be applied over very light or flash rust without detriment.

02. The paint can be applied to damp surfaces. See the technical documentation for references to what they mean by damp. They distinguish between moist, damp, and wet surfaces.

03. You need to buy the Standard Jotamastic 87 paint for use in ambient temperatures above 10degrees C and the Winter grade for temperatures below this. NOTE The above instructions refer to the standard grade, setting & mixing times for the Winter grade are different!

04. I derived the figure of 11% by weight of pot B to pot A from the sample weight charts supplied with the paint and also available on the website. Check this yourself!! Note that no instructions of any sort are on the paint cans themselves.

05. I used 1L mixpots about 2/3 full and I was able to apply it in about 45 to 75 mins depending on the awkwardness of the surface. This gives about 6 mixes per 4.5L pot A tin. Other people may be faster than me.

06. It is said that it is possible to mix the whole of pot B into the whole of pot B (there is room in the pot A tin) and apply the lot in the 2 hours. I suspect this needs a team of people applying it.

07. One 4.5 L tin of Jotamastic 87 is just about enough to provide 1 coat on my 60ft narrowboat (excluding baseplate & uxter plate). I used three tins to provide 3 coats.

08. Other Jotamastic variants exist, as primers, with aluminium, and as top coats etc, but I stuck with plain 87 for all three coats as it claims it can do this.

09. A CWDF member suggested getting different colours to make it easier to see when putting subsequent layers on. I did not do this and it was at times very hard to distinguish so that may be the best thing to do.

10. I used a new brush for each mix, using cheap use-once-and-throw-away brushes from Toolstation at 63p each. These did shed the occasional hair as you would expect but I ignored these as there is little time for such finesse.

11. I did this blacking over an unknown previous two-pack blacking, applied by my boat-builder 5 years ago. This blacking was still good over much over the boat but peeled off easily in some small areas particularly near the anodes leaving perfect metal visible.

12. The edges of the good blacking were sanded down but not brilliantly and when painted with J87, the edges in some cases curled up which is not good. There is a limit to what I can do so I mostly broke these off and applied more paint.

13. Most of the surface preparation was done with a Ryobi Orbital Sander using 120grit discs. I think 80 would have been better but I did not have any available. Rusty bits were attacked with a 4.5” angle grinder using a bevel wire brush. This got rid of loose rust but did not get into pits very well. I did not use it more extensively as the vibration of the grinder (a brand new Erbauer) was more than my hands can cope with for very long. I believe the Jotamastic instructions warn against wire brushing producing a too highly polished surface that reduces adhesion but I have not checked this.

14. Initial cleaning was done with a jet wash by a third party.

15. All the retained blacking was sanded. The dust was taken off one part with a vacuum cleaner with brush, another by washing, and the rest by brushing with a dry sponge. The dry sponge appeared to do the best job and the wet wash the worst. None of them were impressive.

16. Of the corrosion found, 90% was caused by damage to the paint surface. The principle causes seem to be rubbing against tyres used as mooring fenders, and hitting stuff, particularly a stop gate on the BCN (Thame Valley?) that was half open and not seen.

17. I don’t know how much damage was caused by moving through ice as I avoid doing it. I do not know if any was due to passing traffic through ice as I moor online with either side facing the traffic. The damage was markedly more on one side of the bow than the other.

[Dalslandia]

I must say that after water, Jotamastic is the best thing happening the boating comunity.

[blackrose]

I couldn't get through all those instrutions! I can't help thinking you're making it sound much more difficult than it actually is.

 

I used Jotamastic 87 at work for a couple of years, measuring out small amounts. We always mixed by volume rather than weight.

 

When I used it on my own boat I just mixed up a full can which covered one side of my boat. Much easier than all that messing about trying to get the proportions correct. This was standard grade rather than winter grade which cures quicker. I got the full can on the boat by myself in about 2 hours. I would recommend standard grade assuming your working temperatures are above about 10C. The difference is the hardener. The paint (part A) is the same.

 

The main thing to remember when using Jotamastic is to mix part A thoroughly before you add part B. Jotamastic 87 with aluminium is full of metal and you'll spend 20 mins mixing before you can add part b. Forget the drill mixer until this is done, you'll just I burn out your drill!

Edited July 22, 2015 by blackrose

[system 4-50]

I couldn't get through all those instrutions! I can't help thinking you're making it sound much more difficult than it actually is.

 

I used Jotamastic 87 at work for a couple of years, measuring out small amounts. We always mixed by volume rather than weight.

 

When I used it on my own boat I just mixed up a full can which covered one side of my boat. Much easier than all that messing about trying to get the proportions correct. This was standard grade rather than winter grade which cures quicker. I got the full can on the boat by myself in about 2 hours. I would recommend standard grade assuming your working temperatures are above about 10C. The difference is the hardener. The paint (part A) is the same.

 

The main thing to remember when using Jotamastic is to mix part A thoroughly before you add part B. Jotamastic 87 with aluminium is full of metal and you'll spend 20 mins mixing before you can add part b. Forget the drill mixer until this is done, you'll just I burn out your drill!

Agreed, it does come over as a bit of a hassle. I made a list of absolutely everything, then a reader can pick and choose what matters to them. Seemingly inconsequential items made a big difference for me. For example, discovering that the instructions were not on the can cost me two days as I had no means of obtaining them at the time. I don't think it was too difficult to apply, the hard work was in the preparation, but I don't know how you managed to get that much on in the time! But then I'm ancient and have never been an athlete.

[blackrose]

Agreed, it does come over as a bit of a hassle. I made a list of absolutely everything, then a reader can pick and choose what matters to them. Seemingly inconsequential items made a big difference for me. For example, discovering that the instructions were not on the can cost me two days as I had no means of obtaining them at the time. I don't think it was too difficult to apply, the hard work was in the preparation, but I don't know how you managed to get that much on in the time! But then I'm ancient and have never been an athlete.

I wouldn't try to get a full can of winter grade on by myself, but you have a lot more time with standard grade and the rate of curing is very temperature dependent. The only problem with using standard grade is that the boat has to stay out the water for a week after painting to fully cure. I think it's probably 3 days with winter grade.

 

I got 4 coats on in 4 days by myself (2 coats of 87 with aluminium and 2 coats of 87 black), but I was knackered at the end of each day.

 

The data sheets are available online if anyone needs them.

 

http://www.jotun.com/me/en/b2b/paintsandcoatings/products/jotamastic-87.aspx

Edited July 22, 2015 by blackrose

[peterboat]

I am glad I used zinga ok you have to shotblast but when totting up the cost including four new anodes it was £3000.00 the tar free IMO blacking takes three days to cure. Castleford boatyard after using the Zinga are going to drop the epoxy system they were very impressed with the ease of application of Zinga and the reality was it was the same price for materials.

Myself I only did the Zinga because I have seen the results on a boat after 8 years or so its a gamble whatever we use

Peter

[blackrose]

My Jotamastic job cost me £1250 all in (dry dock, gritblasting and paint), but that was doing the painting myself.

Edited July 25, 2015 by blackrose

[peterboat]

They used two and a half tons of glass 2mm chunks to clean it down after it was finished it was like a pure white sandy beach in the drydock. It took 3 3 days to achieve the correct finish for the zinga not something I want to do twice

 

Peter