How much acid in bath?

[sswee]

You might find (like I have) that the LCD acid being very weak means that the voltage to get the 2amps flowing is quite high, maybe higher than your supply can deliver. This problem gets worse for small parts. It's a simple matter of adjusting the current to get a usable voltage and re-doing the calculation to find the time. Use the constant CURRENT setting of the supply.

A slight flaw in what is causing what. The acid concentration has a direct effect on the level of voltage as it is part of the resistance in the circuit. Ohm's law dictates that. The real reason for a PS to max out using the numbers you gave in the example is that you are running the part at a 14 ASF current density.
SS

[Slip666]

Is there anyway to measure the amount of acid in the bath with a hydrometer or something?

[sage]

No flaw. What you said is what I said. The resistance of the bath is high (becasue the acid is weak). Pure water would be the ultimate in high resistance.
High resistance means you need high(er) voltgage to get the current flowing. I=E/R (ohms law) like you said.
The fact that I'm demanding a higher current (14Asf) means I also need a higher voltage for the given acid. More than my supply likes to put out.
The only way to counter this is to lower the resistance by more square inches (more parallel paths for current to flow) or stronger acid.

Sage

[sage]

Is there anyway to measure the amount of acid in the bath with a hydrometer or something?

Yes. As I posted elsewhere in another thread.
Caswell LCD 3:1 solution is about 1.075 specific gravity
the od method 2:1 solution is about 1.100

Search the other threads for my posts. I have a lot more info supporting this there.
I do point out that specific gravity doesn't change too much for normal anodizing solutions but it's a simple way to get on track as to what your solution might be.

Sage

[cameraman]

no appreciable drop in voltage over any reasonable time

I've noticed that larger surface areas (300-400+ in²) produce curves with appreciable, steady voltage drops.

I just find it easier (always have) to think about the amp-minutes required to get the job done. No calculators required.

I'm not seeing that. Let's say I want to anodize 223 in² at 9.3 amps. I suppose the 223 * 5 = 1115 is easy enough, but who would want to divide 1115 by 9.3 in his/her head?? The 223 came out of the computer anyway so I'm already sitting there, and I log all of my anodizing runs into the computer. If I have to do that 3 or 4 times to come up with an acceptable anodizing time, forget it - I already used up plenty of brain power designing the 223 in² part.

Forget the peak voltage thing.

I have to disagree with that sentiment. I know that I'm not going to see the exact same peak voltage as the calculator produces, but I know that it's a guideline that is good within 3-5 volts for my tank. I know that when the voltage is outside that range that it's indicating a problem: too high, my connection is failing. Too low, I'm likely not getting good surface agitation.

You didn't address agitation in your posts. Most of my anodizing has been done at a CD of 4.5 a/ft². Lately I've tried pushing it to 6 a/ft² and have discovered that I quite simply do not have sufficient agitation to pull it off successfully. I shudder to think what kind of agitation I'd have to produce to use a 14.4 a/ft² current density - I have visions of acid splashing out of the tank . The remaining acid would probably fume into the air from the excessive heat generated. I'm not sure I could even do it for irregularly shaped parts, leaving dead zones of dissolution which would defeat both the aesthetic and functional purposes of anodizing in the first place.

Your method causes parts of different size to be anodized at different current densities. You said "current your supply and connections can handle", so knowing that my .045 wire can comfortably handle 2 amps but begins to warm up above that, I'd choose 2 amps for both my 20 in² part and my 30 in² part. The first part would anodize at 14.4 a/ft² and the second at 9.6 a/ft². Since they will have different pore sizes, will they not come out of the dye at different shades? Too close? How about a 60 in² part, at 4.8 a/ft²? If the parts are going different places, fine, no issue, but if the parts will be together making something else, no good.

If your method works for you, great, more power to you, but I'm not seeing any benefit to it and it appears to me that it has the potential to create a slew of problems, especially for someone who doesn't thoroughly understand the process: 2 amps for 20 in² sounds completely reasonable to a new person, but my 10 amp 30 volt supply wouldn't be able to do it - and yet I can do 64 in² in 2 amps, and I can do parts from 10 in² to 405 in² with no trouble at all.

[sage]

[QUOTE=cameraman]I've noticed that larger surface areas (300-400+ in²) produce curves with appreciable, steady voltage drops.

I never do pieces that large. I suppose that's why I've never seen the slope. Nice to know it exists I guess. I don' find it particularily useful though.

>>I'm not seeing that. Let's say I want to anodize 223 in² at 9.3 amps. I suppose the 223 * 5 = 1115 is easy enough, but who would want to divide 1115 by 9.3 in his/her head??


I'm not disputing the fact that the calculator is going to be easier. You picked a pretty screwey number (9.3). I'd just use ten amps amd be done with it. The math is easy then and on a piece that large the .7 isn't going to make much difference.

>>know that when the voltage is outside that range that it's indicating a problem:

Your right on that count. I use the voltage for that kind of thing too. But I don't watch it as an indication of when the anodizing is done, which was, as I understood it supposed to be the reason for the calculator generating the voltage reading.


>>You didn't address agitation in your posts.

So far because of the small pieces I've just been stirring the bath every few minutes. As a matter of fact, just to day I tripled the size of my tank (still small about 3gal) so I'll be installing a pump. I've had no real problems so far. I watch it closely. No drastic thing like you mention going on.


>>Your method causes parts of different size to be anodized at different current densities.

I'm going to assume you mean different size parts in the same bath. If this is what you mean then - No it doesn't. If you think about it a bit, if you have total current of say three amps going into the tank the current will divide itself up according to the resistance of the path to the each part, which is directly proportional to the parts size. Therefore the current to each part and therefore the amps/sqin is self regulating per part.
Please understand that this is within reason of course. I'm not saying that a bath with a piece 100 sqin and another piece 2 sqin won't have problems. But I've always put all the pieces of a project that I want the same colour into the same bath (small quantities) and thre is quite regularily a ratio of 20:1 in size difference and they all come out the same colour.

If you were speaking about doing separate runs of the same part then yes, you'd need (as always) to make sure the CD i(and everything else is the same for each run. That's a given for the reasons you mention.

>> You said "current your supply and connections can handle"

Sorry I've repeated these notes in a couple of threads. I also should have added "within the normal range of anodizing" which for me is betwen 4.5-12 A/sqft). I wasn't suggesting you supply current based only on the wire size to speed up the process.


>>If your method works for you, great, more power to you, but I'm not seeing any benefit to it .

My method isn't really any different. If you juggle calculator a bit you can get it to come up with the same numbers I get - albiet with a bit higher - but not unreasonable CD's.

Sage

[sswee]

[quote=caswellsage]Your right on that count. I use the voltage for that kind of thing too. But I don't watch it as an indication of when the anodizing is done, which was, as I understood it supposed to be the reason for the calculator generating the voltage reading.

There is a misunderstanding if that is the way you took the purpose of the voltage calculation. It is given as a reference only. Using the voltage to determine anodizing time is only done when anodizing by PAR and maybe CV anodizing. There have been a number of posts discussing anodizing by PAR and CV but they are not recommended methods. Anodizing by the 720 rule uses the CD used and desired thickness of coating in mils to determine the anodizing time, not the projected peak voltage.


Sorry I've repeated these notes in a couple of threads. I also should have added "within the normal range of anodizing" which for me is betwen 4.5-12 A/sqft). I wasn't suggesting you supply current based only on the wire size to speed up the process.

To a novice, several of the things you have said are misleading if they do not understand the process to begin with. The standard LCD anodizing is done with 3-6 ASF and a 1:3 acid ratio. Many of us with experience use CD's outside of this standard but we also keep in mind that we're dealing with people just learning. The multiply by 5 amp-minutes and divide by whatever amps your PS and connection will handle to get the time of the run you want is careless when dealing with novices. I know these are not your exact words or how you meant it but you understand what you are doing and they don't. I understand that you've taken the 720 amp-minutes per square foot and broken it down to 5 amp-minutes per square inch. It's when you get to choosing the amp setting that I see a problem. Cameraman has experience and you see the confusion he had. I had to reread the post several times myself to see what you were doing. Imagine someone not familiar with the process.
SS

[sage]

Well, I'm glad someone undertands what I'm doing and that I wasn't really proposing anything REALLY different.
You're right, I guess for someone trying to gather info it can be confusing to see another method (or view of the same method) introdced, so I'll just step aside and live with the process the way I choose to use it.
The anodizing by PAR , I thought, was being proposed by Caswell, along with their LCD method since it is included at the end of their manual. The LCD process works well and they have definately simplified the process using it. It does have it's limitations. But I'm not so sure introducing the process of PAR is a good thing. I've not been able to prove that it works - at least for small batches like I do. (Apparently someone has shown that it is dependant on the size of the batch (current), making it even more difficult).
The 720 calculator is a good tool to have around. It's also a good thing to understand what your doing rather than rely on tools blindly. It makes it easier to figure out why something isn't working when you know how it works.
I'll go back in my cage now.

Thanks guys
Sage

[cameraman]

It's also a good thing to understand what your doing rather than rely on tools blindly. It makes it easier to figure out why something isn't working when you know how it works.

That is suitable for framing and is a universal truth. For some reason it's not readily apparent to the casual observer.

argument: A set of statements in which one follows logically as a conclusion from the others

argumentative: Given to arguing; disputatious

It's a subtle difference, but my intent was the former, not the latter. I understand what you're doing and don't believe I was confused (although I could be so confused as to not even know that I'm confused).

When I learned to scuba dive, the instructor told us "a new diver shouldn't dive below 60 feet". Well, it turns out that there are no scuba police and there's nothing magical about 60 feet - there's really no discernable difference between 60 feet and 70 feet. The value in the statement for a new diver is that it's a number that is displayed on a gauge. It's more accurate to say "dive within your comfort level" but that just isn't much help to a new diver whose comfort level may begin dropping when s/he's bobbing on the surface.

Likewise, the LCD process lays it all out very definitively: armed with a CC supply, the 720 rule, and the checklist you just can't muck it up. The hardest part for me was learning what in the heck PAR, CC, CV, CD, ASF, M-O-U-S-E stood for and that oh, by 'good connection' you meant 'good connection'..

I believe that the PAR stuff is in the manual for those who aren't prepared to drop a couple hundred bucks on a CC supply and are going to give it a go with battery charger and light bulbs.

"I'll just step aside"
Please don't - that would be a loss to the board, and after you've done a few runs with your 3 gallon I'm going to have a couple questions for you. The point that I was trying to make (apparently inadequately) is that "That's a given..." isn't defined yet for rick201.

They let you out of your cage?? I have to type through the bars .

[sswee]

caswellsage,
Take no offense as none was meant. There are discussions on methods and ways outside the box, we just need to preface it as such so newbies don't start out on the wrong foot.
As cameraman stated, the more members the forum has the better for us all.
I used the PAR method when I first started with a battery charger and light bulbs. The results were poor to say the least and definitely inconsistent. Learning about it to better understand the process was beneficial for me but to use it in actual practice, I see no benefit at all.

If I neglected to do so already, welcome to the forum.
SS