Is it Comastic and how much do I need?

[Daltonia]

I'm planning to re-black my 58' and 10' narrowboat this summer. It was built in 2014 and originally blacked with Comastic. I've owned it since Aug 2017 and nothing in the paperwork suggests it was re-blacked since new. However, I'd like to be sure before re-blacking with Comastic. How do I check that the current surface layer of blacking is Comastic? Also, approximately how much Comastic would be needed for two coats of the sides plus a third coat along the water-line (I don't plan to re-do the bottom)? As always, many thanks for your valuable help :-)

[Neil2]

Presumably you just want to check if it has been blacked with a bitumen based product?  Wipe it over with a cloth soaked in white spirit.  If the black comes off it's bitumen.

[Daltonia]

21 minutes ago, Neil2 said:

Presumably you just want to check if it has been blacked with a bitumen based product?  Wipe it over with a cloth soaked in white spirit.  If the black comes off it's bitumen.

Thanks. I've just cleaned a bit close to the water-line then waited for it to dry. Then rubbed a kitchen towel across it with a dab of white spirit. The towel became black. I then scraped a little of the blacking off and put it in a dish with a little white spirit. It dissolved. Does this mean the current surface layer, at least, is not Comastic but is a bitumen-based product?

[Neil2]

14 minutes ago, Daltonia said:

Thanks. I've just cleaned a bit close to the water-line then waited for it to dry. Then rubbed a kitchen towel across it with a dab of white spirit. The towel became black. I then scraped a little of the blacking off and put it in a dish with a little white spirit. It dissolved. Does this mean the current surface layer, at least, is not Comastic but is a bitumen-based product?

If it definitely dissolved then it must be bitumen.  It's not unusual for a comastic boat to be coated with bitumen, a lot wouldn't even know the difference, but you can't do it the other way round so if you have a "blacked" hull you have to either stick with it or have it removed.  

[Daltonia]

1 hour ago, Neil2 said:

If it definitely dissolved then it must be bitumen.  It's not unusual for a comastic boat to be coated with bitumen, a lot wouldn't even know the difference, but you can't do it the other way round so if you have a "blacked" hull you have to either stick with it or have it removed.  

Ah, I see, thanks very much. I was originally planning to use Intertuf 16 until I found out the original blacking was Comastic. It seems the Intertuf may again be a reasonable choice?

[Sea Dog]

3 hours ago, Neil2 said:

Presumably you just want to check if it has been blacked with a bitumen based product?

And also, being as it's cited as having a 10' beam, if it's actually a Narrowboat!

[ditchcrawler]

4 hours ago, Sea Dog said:

And also, being as it's cited as having a 10' beam, if it's actually a Narrowboat!

And you only bought it this coming summer (cant find the smillies)  

Edited April 10, 2017 by ditchcrawler
Found it