Oxy-act gas variations 2

[rollernose]

I am using an oxy-act torch to heat patina mild steel art work. I've been having problems getting consistant color results. Sometimes I'm able to get vibrant tones of blueing,
sometimes not. I seem to have problems when I switch bottles. Is there a chemical make up differance in the flame from a full set of bottles as aposed to a half full set?? Are there different grades of gas or variables from bottle to bottle?

Thank you,
Rollernose

 

[tomwalz]

Yes, there probably is.

Acetylene is made to burn primarily just to get really hot. My guess is that your application is a lot more sophisticated than straight burning. Commercial acetylene is extremely well made for its intended use. It may not be as suitable in a much more sophisticated operation. Examples: 1. We use a ruler in the office and micrometers in the shop. The rulers are much more than accurate enough for office use but you cannot use them to measure to hundredths in the shop. 2. We use extremely pure ‘reagent grade’ materials in the lab but in the plant we use the same chemical in the much less expensive commercial / industrial/ etc. grade.

Stainless steel is also a chemical compound. It is made so that the surface oxidizes and it becomes ‘stainless’. Not all of it becomes equally stainless at an equal rate.

Figure that for acetylene and stainless steel in their intended uses you need a quality value of 50. (That’s just a number I picked – doesn’t mean anything.) Anyway, these products are made with quality values in the 80’s and 90’s. No matter how bad any individual batch is it will still be much better than required. Now you come along and you need a value of 85. Sometimes you get 95 and sometimes you get 80 in your tanks of gas.

Having said this, the first thing I would look at if I were you is the regulators. Have them checked and see how accurate they are. While you are doing this you could also examine your studio for sources of heating and cooling; breezes, sun coming in windows, furnaces that kick in and out creating drafts. Are results different first thing in the morning compared with the mid afternoon? Does what it is resting on work as a heat sink? Does it make a difference if you preheat the material? (The first time in the morning you are working on cold material and heating it rapidly. As you continue to work you are preheating adjoining areas and actually heating them more slowly, over a longer time. Also, as you move left to fight then the areas at the top and bottom of you working area get heated then cooled before the final heating.)

tom

 

[rollernose]

Thanks Tom,

I,m using the same preheat and coloring tech. as always, but all of a sudden my ability to get the desired results from them have changed. That change came with the hooking up of the new bottles so of course thats the area of my focus to find the problem. The temperature of the shop has gone down so I will address that next.


Thanks for help
Rollernose

 

[TheBlacksmith]

Do you have single stage or two stage regulators? Single stage are more suspectible to change as the bottle pressure changes, in your case from nearly empty to full. Two stage regulators are used for continuous operation where constant output pressure is important.

Blacksmith