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TOPIC: Jotamastic alternative

Jotamastic alternative 06 Jul 2018 09:42 #99664

Have a look at Jotun website and Hardtop XP.
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Jotamastic alternative 05 Jul 2018 11:01 #99646

>Having gone to the trouble of blasting back to steel and epoxy coating the hull, it will be a shame to compromise.

I agree with Chris. I wouldn't put single pack on after all that expense.
Jotun appear to do a Jotamastic Smartpack which is a smaller set and mixed 1:1 by volume.
I wouldn't worry about the theoretical full hardening time. It seems that you will be applying it above the waterline.
I don't know where you are, but in UK Jotamastic is a pretty good deal from Bayside Marine, and any other Jotun product. Around £50 for the 5ltr pack. Makes it considerably cheaper than Epifanes.
I've used Jotamastic AL87 and it is quite a thick product and designed for spray application or brush. Really doesn't like a roller.
My hull was airless spray painted with a Spanish 2 component product in 2005. It was a high phosphate primer and left at that. I used the same stuff to touch up over the years. When I repainted above the waterline in 2014, I used another 2 component paint. Shipcoat NL Epoxy Tar Replacement as the Spanish was no longer available. Great thing about ETR is that it has a long pot life and rollers on really well.
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Colin Stone
KEI
www.luxe-motor.kei.co.uk

Jotamastic alternative 04 Jul 2018 09:01 #99641

Following up on Chris's comment, another thing to know about Jotamastic is that it dries slowly (4 days to a week before water immersion depending on the air temps and whether you talk to the UK or French rep), which can make it a poor choice as a touch up paint depending on where you plan on using it on the boat. Though the paint has likely polymerized early on, it is physically soft and prone to damage until the solvents out gas and it hardens. For a pit stop in a dry dock it may not be the best choice. In our case I'm referring to specifically to Jotamastic 87.

The above the waterline single pack Epifanes was applied weeks after so the Jotun had an opportunity to thoroughly out gas. Where it was applied properly the system performed well, as judged by thorough adhesion tests taken during a paint survey. Though there were failures to the metal where the Jotun was applied improperly, there has been no indication of a failure at the interface between the Epifanes and the Jotamastic 87.

As it might be informative I've attached three photos that show how the Jotun grays over time. One picture shoes the waterline established between Epifanes Multiforte (upper) and the Jotamastic 87 (lower) soon after application. Picture 9577-1 was taken about 6 weeks after launch and about 3 months after application of the two coatins and shows distinctive graying of the lower Jotun paint. 1400-1 shows the waterline the Epifanes and Jotun when the coatings were about 3 years old. Near the waterline there's generally graying from the limescale, but the Jotun below the waterline has grayed more.

To re-emphasize my point: Jotun makes an excellent base coat for the bottom but it not ideal for a variety of reasons above the waterline maintenance. I personally would recommend migrating to a quality single pack, accepting for the time being that the patches will not match. At the next blacking use an easier to maintain paint above the waterline.
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Jotamastic alternative 04 Jul 2018 00:42 #99639

Generally speaking, apply two-pack over two-pack and single pack over single pack paint.
You can usually get away with applying single pack over epoxy two-pack, but solvent entrapment can cause problems. However I would not recommend sandwiching single pack paint in between two-pack as solvent entrapment is much more likely when another layer of two-pack paint is applied over the top.
This means that once an epoxy coating is applied; stick with the same two-pack system. Having gone to the trouble of blasting back to steel and epoxy coating the hull, it will be a shame to compromise.
I also advocate mixing small quantities using digital kitchen scales, and keep a calculator handy to work out the correct amount of part B.
One further comment, if you are using Wintergrade part B, do not mix up large quantities (more than a litre at a time). In this weather there is a risk it will go off before you can apply it…
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Jotamastic alternative 03 Jul 2018 15:35 #99634

I use Jotun 2 component paint and have no trouble keeping it and using it beyond its shelf life.
I've got some 2 component Sigma primer and De Ijssel Double Coat that dates back to 2005 and all are fine.
Just keep it cool in the bilges.
For mixing any quantity, I now use digital kitchen scales - use when Mrs is out shopping!! Much more accurate than mixing by volume.
Peter Jones at Jotun UK head office should be able to tell you how many grams of each are required. Eg for XP Hardtop 100gm of paint needs 8 grams of hardener. So for touching up I go down to 12 gram paint and 1 gram of hardener. For really small quantities, drug dealing scales are needed!
Although 2 component can be considered a phaff with the mixing etc, I prefer it to single pack with the thickening and skin etc.
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Colin Stone
KEI
www.luxe-motor.kei.co.uk

Jotamastic alternative 03 Jul 2018 15:25 #99633

I'll reply again on this side.

You have a wide range of options as Jotun says that subsequent coats can be polyurethane, polysiloxane, epoxy, acrylic, or vinyl epoxy. If you are shopping at a typical chandler you won't have many options. The downside is that your Jotun has likely grayed and will continue to gray with time. Depending on how picky you are, finding a touch-up paint for the above the waterline areas that does not stand out will be near impossible, even if you applied more Jotun. Personally I would look for a single pack polyurethane marine paint and accept that you are just applying it to hold down the rust until the next re-black.

Consider the longer term and what you want to do in the future. Now that you have the solid Jotun base applying a single pack over the top on routine repaints is a reasonable option for the foreseeable future. But if you do maintenance with a single pack polyurethane then application of more Jotun over the top is problematic, or so I'm told. What you apply now can influence what you are going to do in the future.

Epifanes Multiforte is a decent urethane option, but I've never found it in small cans. Epifanes says that it can be stored for 3 years.
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Jotamastic alternative 03 Jul 2018 13:27 #99631

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About 12 months ago when we bought our barge we had it shotblasted and coated in jotamastic 87 below the rubbing strake.Over the ensuing time we have gathered some scuffs/scratches which I want to touch up to protect the steel. From speaking with Jotun I do not seem to be able to buy a small quantity of the 2 pack only large tins (5Ltr) which have a relatively short shelf life and will take up scarce storage space.
Anybody know of alternatives?
Thanks

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