1. Forgot camera was in JPEG >.<
Should be able to see well enough though. This is the part I had in for a tad over 72 mins (by accident).

2. Originally Posted by JOGARA
Fusion 360 but can't work out surface area for some reason.

I have 5L tubs. Only 3L of water plus added ingredients.
By weight I have 3000g of water and 400g of 85% acid. So that is 7.5% of 85% acid?
Rarely see suggested ratio by weight, usually by volume.

However, simple enough to figure out an approximation I guess. 3kg of water is 3L, for the sake of simplicity we'll say your 400g of 85% acid is actually 340g (400 * 0.85) and ignore the extra 60g of water, which when considering the specific gravity of sulphuric acid is 1.85 should mean it was about 184ml.

So you have actually got 0.184L acid to 3L water, or roughly a 1:16 ratio which is not too far off what I've seen recommended for 6asf (slightly low perhaps), but more than a little on the low side if using 4.5asf (caswell recommend 1:3 battery acid/water, or around 1:11 acid/water if my maths holds up).

That jives more with what you would expect - too low a concentration will give a smaller pore size which is bad for dying. Were you calculating with 4.5asf or 6asf out of interest?
Last edited by Zeeflyboy; 15-10-2017 at 02:50 PM.

3. Oh and fusion will give you surface area very simply - just use the menu on the left, select the body in question and right click - properties. First property is area.

4. Originally Posted by Zeeflyboy
Rarely see suggested ratio by weight, usually by volume.

However, simple enough to figure out an approximation I guess. 3kg of water is 3L, for the sake of simplicity we'll say your 400g of 85% acid is actually 340g (400 * 0.85) and ignore the extra 60g of water, which when considering the specific gravity of sulphuric acid is 1.85 should mean it was about 184ml.

So you have actually got 0.184L acid to 3L water, or roughly a 1:16 ratio which is not too far off what I've seen recommended for 6asf (slightly low perhaps), but more than a little on the low side if using 4.5asf (caswell recommend 1:3 battery acid/water, or around 1:11 acid/water if my maths holds up).

That jives more with what you would expect - too low a concentration will give a smaller pore size which is bad for dying. Were you calculating with 4.5asf or 6asf out of interest?
Dam it I already diluted half my mix. I got loads of everything so can make a proper batch using fluid measuring.
I didn't account for the acid being heavier than the water. I thought it was near enough and it being 85% I could within range say that it is 100% and the extra weight would offset that xD

I guess this is why I am having problems then...
Last edited by JOGARA; 15-10-2017 at 02:53 PM.

5. Yeah sulphuric acid is nearly twice as dense as water (1.85g/ml vs 1g/ml)... easy mistake to make.

From what you've said, you definitely seem to have far less than recommended for 4.5asf by cadwell's guide. You aren't that far off what I've seen recommended elsewhere for 6asf though.

It is certainly a potential explanation, one of the side effects of too low a concentration is small pore size which then can give issues taking a dye.

Did you see my second post about fusion btw? Few clicks to get area of a body... copy to clipboard and ask google to convert the area value to square feet, multiply by number of the parts you are doing at once and then desired amps per square foot.
Last edited by Zeeflyboy; 15-10-2017 at 03:00 PM.

6. I think I need to start from the beginning. I have read through a few of the guilds and have gotten mixed up a bit with everything.

From what I have gathered, 6asf is only really for dark colours with large dye molecules, 4.5asf works for pretty much everything?
I should have for 4.5asf a 20-25% acid concentration?

What am I better off doing for my process? I am dyeing black and need it to be a tough enough for a product case that might be battered a bit.
Ill mix up a new batch, using scales but account for the higher weight and concentration.
Last edited by JOGARA; 15-10-2017 at 03:18 PM.

7. Hang on. I am using Phosphoric not Sulphuric.

Did I mess up?

8. Well you can anodise using phosphoric, but all these guides are based around the use of sulphuric acid. I don't really know much about phosphoric acid anodising but I certainly wouldn't assume the processes are the same regarding concentrations/time/current etc, nor in it's ability to take dyes afterwards.

And no, 20-25% is far too high (for sulphuric, no idea about phosphoric). The caswell guide says 3 gallons water to 1 gallon battery acid, but battery acid is typically only around 32% - when you run the maths that works out to around 1:11 or approximately 9% by volume.

I don't think there is any problem using 6 asf as long as the concentration is appropriate. I have never seen any suggestion that it will struggle to take dye. If you ran 6asf using the same concentration as for 4.5asf then you would potentially end up with a smaller pore size... if you use a lower concentration of 1:15 then you should end up with similar pore size to the 4.5asf at the higher concentration.

edit, out of interest:

Phosphoric acid anodizing is basically used for structural adhesive bonding in high-humidity environments. This process is known as the Boeing Process and is carried out at 10-15 V. The formed oxide film has a greater durability under adverse conditions than film formed in chromic acid and sulfuric acid. One of the reasons for the great adhesive property is said to be due to the morphology of the oxide film, which should be a film of pores with whiskers or protrusions on the top surface of the formed film.
Sounds like the morphology of the surface is different which makes it particularly suitable for adhesives... if the morphology is that significantly different then it could certainly prevent the acceptance of dyes.
Last edited by Zeeflyboy; 15-10-2017 at 04:00 PM.

9. ## The Following User Says Thank You to Zeeflyboy For This Useful Post:

10. Off to go buy some battery acid then :p

Thanks

http://www.ebay.co.uk/itm/161904105341

Used these guys last time for my other acid.
Last edited by JOGARA; 15-10-2017 at 05:06 PM.

11. Yeah so with that, to do 4.5asf as per caswell guide you would mix 1L of that to 3L distilled water.

You can get 1L of 98% sulphuric acid on amazon for that price, but there is an argument to be made that buying battery acid is safer. Sulphuric Acid Pure (H2SO4) Min. 98% 1*Litre https://www.amazon.co.uk/dp/B013T3EO..._Nk74zbXPCQA3M

If you go the 98% route needless to say you need to be effing careful with it, especially when mixing with water.

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