paint ratio

[dsw]

Paint ratio 3.5 to 1 volume ?
Jotamastic 90 anyone know what weight of comp A
And comp B is for 1 ltr mix ?
or a simple way of measuring it ?

 

[PCUK]

Fill a container with 1 litre of water. Put a stick in and mark the 1 litre position.
Then make nine equal marks on the stick up to the litre mark. Then use seven marks for paint and two marks for hardener.
Or get a paint measuring pot.

 

[VicS]

Paint ratio 3.5 to 1 volume ?
Jotamastic 90 anyone know what weight of comp A
And comp B is for 1 ltr mix ?
or a simple way of measuring it ?

If you look at the safety data sheets you will find that the density of component A is 1.457 to 1.607 g/cm³ and of component B, 1.01 g/cm³ ( 1.0g/cm³ for the wintergrade

You can now calculate the mixing ratio by weight

 

[dsw]

Fill a container with 1 litre of water. Put a stick in and mark the 1 litre position.
Then make nine equal marks on the stick up to the litre mark. Then use seven marks for paint and two marks for hardener.
Or get a paint measuring pot.

got a pot with 2:1 3:1 4:1

 

[dsw]

If you look at the safety data sheets you will find that the density of component A is 1.457 to 1.607 g/cm³ and of component B, 1.01 g/cm³ ( 1.0g/cm³ for the wintergrade

You can now calculate the mixing ratio by weight

with a little help from someone with more brains than me we came up with
1221g of A and 222g of B = 1443g but would like that confirmed by someone
like you vic ? and it is the WG

 

[VicS]

with a little help from someone with more brains than me we came up with
1221g of A and 222g of B = 1443g but would like that confirmed by someone
like you vic ? and it is the WG

3.5 : 1 is the same as 7 : 2

To make 1 litre you need 7/9 litre of A and 2/9 litre of B

1 lire of A is 1457 g to 1607g.
7/9 of a litre will therefore be 1457 x 7/9 = 1133g , to 1607 x 7/9 = 1250g

1 litre of B (wintergrade) is 1000 g
2/9 of a litre will therefore be 1000 x 2/9 = 222g

However in view of the variation in density of component A I think I would stick with measuring by volume

Mark a suitable mixing container at 7/9 litre and 1 litre. (7/9 litre is 778 cm³)
Measure 778 cm³ component A. then add component B to reach the 1 litre mark

I do not like doing arithmetic at 0330 in the morning !

 

[Daydream believer]

Buy a litre's worth & lob the lot in :encouragement:

 

[GHA]

Paint ratio 3.5 to 1 volume ?
Jotamastic 90 anyone know what weight of comp A
And comp B is for 1 ltr mix ?
or a simple way of measuring it ?

Weigh a small amount of A and same amount of B on digital kitche6scales. Multiply weight of the appropriate component by 3.5.
So say 1 unit A weighs 30g, 1 unit B weighs 40g. 3.5A:1B = 105g:40g. Quick spreadsheet will give you different weight ratios for different amounts.

Works great for mixing up small amounts accurately. Should match the SG in the datasheet but there has been an incident told on here where the SG was wrong and a boat needed repainting... Best to check!

 

[dsw]

3.5 : 1 is the same as 7 : 2

To make 1 litre you need 7/9 litre of A and 2/9 litre of B

1 lire of A is 1457 g to 1607g.
7/9 of a litre will therefore be 1457 x 7/9 = 1133g , to 1607 x 7/9 = 1250g

1 litre of B (wintergrade) is 1000 g
2/9 of a litre will therefore be 1000 x 2/9 = 222g

However in view of the variation in density of component A I think I would stick with measuring by volume

Mark a suitable mixing container at 7/9 litre and 1 litre. (7/9 litre is 778 cm³)
Measure 778 cm³ component A. then add component B to reach the 1 litre mark

I do not like doing arithmetic at 0330 in the morning !

so its 778 ml and 222 ml = 1000

 

[PCUK]

Talk about making a mountain out of a mole hill.

 

[dsw]

Talk about making a mountain out of a mole hill.

how do you measure that then ?
and I only wanted to know what 3.5 : 1 was in grams to start with
but now I will measure it in ML

 

[lonederanger]

but now I will measure it in ML[/QUOTE]

I would advise against that, it is much easier and accurate to weigh by weight. I have bought all my jotamastic from SML trade paints they provide a weigh by weight chart for all their jotun range. Unfortunately they are all on the boat at the moment, but i am sure that an easy google search to SML web site will find said chart . It is fairly critical to get the most from your paint film to get an accurate mix to avoid any excess hardener or medium in your mix,

 

[VicS]

how do you measure that then ?
and I only wanted to know what 3.5 : 1 was in grams to start with
but now I will measure it in ML

You did not expect to be able to paint your oil rig ,or whatever you are doing, without a spreadsheet didyou? I expect there is an "app" for it though

 

[dsw]

but now I will measure it in ML

I would advise against that, it is much easier and accurate to weigh by weight. I have bought all my jotamastic from SML trade paints they provide a weigh by weight chart for all their jotun range. Unfortunately they are all on the boat at the moment, but i am sure that an easy google search to SML web site will find said chart . It is fairly critical to get the most from your paint film to get an accurate mix to avoid any excess hardener or medium in your mix,[/QUOTE]

jotun advised me that it should be measured by volume and vicS on this forum
also said the same so as I want to mix a litre at a time I will measure 778 ml of
comp A then add 222 ml of comp B = 1000 ml or have I missed some thing.

 

[VicS]

Here is the chart for measuremnt by weight that Lone Ranger refers to https://www.smlmarinepaints.co.uk/files/library/files/2 pack weights 0314.pdf

Based apparently on the average density of the components. the actual density being dependent on the colour .

You can buy suitable weighing scales from SML https://www.smlmarinepaints.co.uk/accessories/other-accessories/weighing_scales

You can also buy suitable mixing cups https://www.smlmarinepaints.co.uk/accessories/other-accessories/mixing_cup

 

[lonederanger]

You will be in effect mixing by volume ,the chart that VicS has kindly found gives you the weight of the volume of each part. it is relitively easy to measure very small amounts by ml as you can use a syringe, they are accurate and you can get most of the paint from the recepticle. When you try and pour from a 5 litre tin and try and mix say 3/4 litre of that thick sloppy gunk, it is not easy to be accurate. I have not used the new 90 yet ,everything i have done has been useing the 87. It seems to stick well however its is the most difficult thing i have ever tried to paint, it will not flow, it drags, i have thinned it with thinners, epoxy thinner nothing works. If you want to sand flat afterwards its a bugger as it goes hard as a rock. I was advised , and it works that if you wish to sand flat afterwards to put a final sacrificial coat of a softer epoxy as the last coat.

 

[dsw]

You will be in effect mixing by volume ,the chart that VicS has kindly found gives you the weight of the volume of each part. it is relitively easy to measure very small amounts by ml as you can use a syringe, they are accurate and you can get most of the paint from the recepticle. When you try and pour from a 5 litre tin and try and mix say 3/4 litre of that thick sloppy gunk, it is not easy to be accurate. I have not used the new 90 yet ,everything i have done has been useing the 87. It seems to stick well however its is the most difficult thing i have ever tried to paint, it will not flow, it drags, i have thinned it with thinners, epoxy thinner nothing works. If you want to sand flat afterwards its a bugger as it goes hard as a rock. I was advised , and it works that if you wish to sand flat afterwards to put a final sacrificial coat of a softer epoxy as the last coat.

jotun sent me this reply=
I am assured that for a 1 ltr mix of Jotamastic 90 Grey WG the weights will be

A = 1.2055kg
B = 0.2199 kg

Please bear in mind that we manufacture for the mass use market and as such we fill the pack ‘B’ to cope with the highest mix value. The mixing ratio is not usually done by weight but volumes, and usually is for full pack mixes. So when we add comp B we probably have more volume / weight of comp B than is required but this has no detriment to the mixed product.

 

[lonederanger]

Well, you have your answer.
That chart that VicS found did not have the 90WG on it, I am sure mine does i will check at the weekend ,it will be interesting to see if the weights match up.