Hardness of oxide layer

[Ziptie]

Relative newbie here looking for some advice.
I have a pretty good 5 gallon rectangular bucket system that is all home built. I built my own heaters, thermostat wells, ano tank cooler and have had fairly good success with clear anodize on small parts. Lots of tanks with several triple rinses.
I am using titanium racking parts from servi-sure which work great. My temperature control is an issue since I went with
water heater thermostats in submerged rectangular tubing wells. Thought it was a cheaper way to go, but only controls within
about 15 degrees.
Anyway, don't want to get too long winded I am looking to do a product that will require matching colors from one batch to the
next. I started with caswell grey NLN and grey BL with lots of trouble controlling colors. Read some more and went to a black thinking that would be more consistent. The first black parts I did came out the blue/grey I originally wanted. So I think just getting a very consistent process control is my problem. But does anyone have a recommendation for the easiest color to match from one batch to another?
Second question is related and has more to do with ano bath temperature. I did two matching machined 6061 idler pulleys last night racked together. 114.36 sq inches per the pair. Ano bath temp at 60 degrees. Astron 50 amp pwr supply, 15 volts and 9to 9.5 amps for 60 minutes. Current stayed constant and the temp gained maybe 1 degree with the cooler running. Black dye heated to 140 deg for 30 minutes and mid temp nickel seal at about 170 deg. for 30 minutes. Color came out a deep fairly dark navy blue.
I was trying to get as hard a coating as possible. Is the lack of deeper black color due to smaller pore size and a harder coating, which I was trying for, Or lack of pore depth due to the colder ano bath temp. Any expert or experienced opinions appreciated!
I have finally been able to get a good black with 70 plus degree bath temps, so I do know that the colder ano temp is not going to work for good colors.

[acidrain]

The key to matching colors is to ano exactly the same way everytime... that means temperatures too.
Your hardest coating using the LCD method will come from a 1mil build at below 70F.
Once you know the surface area, and amps needed, run those exact amps everytime. It get's complicated with more than one size of part.
Your blacks should be a deep black without chaulky-ness.

I just re-read your post... your amps need to stay steady, and the volts will go up and down as needed. Are you not running in CC mode?

[Ziptie]

Thanks for the reply ! For these parts I just ramped up the voltage over about 15 seconds or so and then just left the voltage at 15v and amperage set to the limit to let the parts draw what they would. Being pretty new to this I thought with the cold ano bath temp the more current the better for a harder layer. Current draw didn't change during the 1 hour time. Is my thinking OK on this? By the parts square footage area the current seemed about right for 11 asf. Anyway that's the most the parts would take. Suggestions or Recommendations?
Just in general by the conditions - 60 deg ano bath - 15 volts and 9.5 amps - 1 hr time - roughly 11 plus ASF - and heated black dye bath - etc. would the lighter color be from smaller, denser pores not taking the dye OR less than 1 mil thickness not taking as much dye , or probably a combination? I know it is a poor way to try to get closer to type III but looking for an experienced opinion so I have an idea what is happening. Thanks in advance for any input.

[gcdrummer02]

you're doing the opposite of what you should do with you power. If you max out the voltage, the parts will just draw what they need. The controlled variable is the amperage. Using the 720 rule you can get a pretty exact value for your thickness.

Monitor your temperature closely also, and you should get consistent results.

[acidrain]

At 11 amps/sq. ft., you are above the LCD perameters. We only know that if you stick to the LCD method, it will work every time with consistant resuts.
It could be that the pores are much smaller, and dye won't take as easily. BUT, what I really think is happening is you are not anodizing what you think you are, and the layer is either too thin, or too soft.
I suggest getting a CC power source with enough amps to do your largest run with volts to spare. Then ano at 6 amps per sq. ft. It will be a little slower, but the consistency will be your reward.