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mbmb

making blacking thicker

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if paint is quite thin [as bitumens go] i want to thicken it a bit as its going onto a narrow boat hull where the paint thickness is the most important thing.  .  its been suggested i use cement powder which would also make it  a bit harder and resist scraping on the canal bottom.  can anyone  foresee any problems with it

 

thanks

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Will probably (drastically) reduce the adhesion, which would not be good. A much better approach would be to apply several coats, with the recommended drying time between, up to the recommended thickness.

  • Greenie 3

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I would suggest it’s better to cover with a number of thin layers as thickening will take a larger percentage off whereas many coats reduces loss over time.

 

if you must thicken try cornstarch

Edited by NB Lola

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Stick it in the fridge for a few hours!

 

What specific blacking are you using? Manufacturer and type please, because the "right" answer depends on exactly what it is, but it won't be cement ...

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I used driveway repair bitumen paint to fill the surface voids on my steep tarmac drive that tends to get eroded unless the surface is waterproof.  I used cement with bitumen, but the only way I could get it to mix was to sprinkle the cement on the surface, followed by sprinkling the bitumen on top and agitating well with a soft broom.

 

Not much help, except I couldn't get the 2 components to mix properly in a bucket, and when I tried to apply the poorly mixed product it wouldn't adhere well.  ..... it would have been hopeless on a vertical surface.

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35 minutes ago, mbmb said:

if paint is quite thin [as bitumens go] i want to thicken it a bit as its going onto a narrow boat hull where the paint thickness is the most important thing.  .  its been suggested i use cement powder which would also make it  a bit harder and resist scraping on the canal bottom.  can anyone  foresee any problems with it

 

thanks

How many coats are you planning to put on ?

 

The norm is 3 coats over 7 days.

1st day to wash and scrub the hull

2nd day to put on 1st coat

3rd day touch up in 'corners' weed hatch around swims etc

4th day 2nd coat

5th day repeat  day 3

6th Day repeat day 4

7th day - relaunch

 

It depends on conditions but ideally you should allow 24+ hours between coats.

  • Greenie 1

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If the blacking is a bit thin then you need to remove some solvent. 

Either:

Leave the lid off, stirring regularly, till it is thick enough- probably a couple of days this weather.

Or : Bring to the boil ( a gas ring might be a bit spectacular so do it outside and preferably handy for the fire brigade  or use an electric plate) and stir until thick enough.

Or: Add solid lumps of roofing bitumen and stir till dissolved/ goo is thick enough.

N

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12 minutes ago, Alan de Enfield said:

How many coats are you planning to put on ?

 

The norm is 3 coats over 7 days.

1st day to wash and scrub the hull

2nd day to put on 1st coat

3rd day touch up in 'corners' weed hatch around swims etc

4th day 2nd coat

5th day repeat  day 3

6th Day repeat day 4

7th day - relaunch

 

It depends on conditions but ideally you should allow 24+ hours between coats.

 

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thanks for the good suggestions/advice. i got the idea from a forum where they threw cement powder of the wet paint [not mixing it] in a dutch boatyard [standard practice at that yard] , whats peoples views on this?

using iko pro bitument which i already have but hear is a bit thin. maybe 3 coats!

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As mentioned above, several thin coats would be better as that will help the bitumen to get into all the pores in the metal.  If you must thicken it just leave the lid off in this heat, the solvent will soon evaporate.

 

 

 

 

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As that's a bitumen containing paint, just use it as is.  It claims to be overcoatable in 4 hours, so just keep painting until you run out of it!

 

If you want more, Wickes have it on special offer this weekend ...

 

Oh, and don't heat it up or it probably will explode!  It's not a traditional blacking, so some of the usual advice is wrong for the stuff you are using.  Just paint it on and do plenty of coats.

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8 minutes ago, TheBiscuits said:

As that's a bitumen containing paint, just use it as is.  It claims to be overcoatable in 4 hours, so just keep painting until you run out of it!

 

If you want more, Wickes have it on special offer this weekend ...

 

Oh, and don't heat it up or it probably will explode!  It's not a traditional blacking, so some of the usual advice is wrong for the stuff you are using.  Just paint it on and do plenty of coats.

am interested to know how it differers from the normal bitumen , are u sure overcoat time is only 4 hours?

how much would a v hull 34 ft take for coat . anyone know?

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6 minutes ago, mbmb said:

am interested to know how it differers from the normal bitumen , are u sure overcoat time is only 4 hours?

Did you get the instruction sheet with it? It probably has a guideline of different overcoat times for different temperatures, obviously a day like today is going to shorten drying time compared to eg mid winter or 10 deg C in springtime etc.

 

ETA I found this info: https://www.ikogroup.co.uk/product/ikopro-black-bitumen-paint/ its a bit vague, saying 2-4 hours drying time. Sometimes paints have a time "window" which is best to overcoat them in, after that you need to further wait until its fully dry. 

 

If its quite thin compared to normal blacking, its going to have a high solvent content, so I'd say just paint it on, by the time you've been round the boat once I bet the 2 hours would be up and you could go round again and again.

Edited by Paul C

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7 minutes ago, Paul C said:

Did you get the instruction sheet with it? It probably has a guideline of different overcoat times for different temperatures, obviously a day like today is going to shorten drying time compared to eg mid winter or 10 deg C in springtime etc.

thanks, very interesting

am still interested to know how it differers from the normal bitumen ,

how much would a v hull 34 ft take for coat . anyone know?

4 minutes ago, TheBiscuits said:

https://www.ikogroup.co.uk/download/57778/

 

Technical data sheet.

 

Drying time: 2-4 hours

 

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I would guess if you are doing gunwhales to the bottom of the V, maybe a coat and a half per 5L tin on a 34ft boat.

 

Don't forget to do inside the weedhatch!

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17 minutes ago, pearley said:

You could try SML Ballistic Black. It's very thick.

Used this earlier this year, didn't get the same coverage as I am used to from Intertuf. The blacking did flow well and I felt that it will do its job well.

With Intertuf  3 coats went on, Ballastic black gave 2 full coats and 1 more along the waterline. This on a 60ft boat. It was also much cheaper almost £50 saving.

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MSDS sheet states it is harmful for aqatic life

Edited by smiler

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1 minute ago, smiler said:

MSDS sheet states it is harmful for aqatic life

So does the info that comes with International boat was & wax. I conclude that is relating to what is in the can, not when it has cured.

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1 hour ago, Paul C said:

Did you get the instruction sheet with it? It probably has a guideline of different overcoat times for different temperatures, obviously a day like today is going to shorten drying time compared to eg mid winter or 10 deg C in springtime etc.

notgytg

yet

any one know how to enter a reply, not intuitive at all

 

just bought 45 litres of it [ less than half price though] , i'll have to paint everybody's boat i think

Edited by mbmb

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3 minutes ago, mbmb said:

notgytg

yet

any one know how to enter a reply, not intuitive at all

 

Type in the box that says "reply to this topic"

 

Edit to add :

Located at the bottom of the page.

Edited by Alan de Enfield

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Just now, mbmb said:

just bought 45 litres of it [ less than half price though] , i'll have to paint everybody's boat i think

OK, don't do what I said and paint until it runs out - I thought you would have 2 or 3 5L tins! :D

 

 

I'd say probably 4 or 5 coats would be plenty, but see how it goes on and how it dries. As you already have it, get a couple of coats on and see what happens.  If you still have 2/3rds of it left when you have finished, flog it to someone else ...

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