Gents;I understand the need to use pure water when making the solution but do you use ordinary chlorinated tap water when cooking off,or do you still need pure water for this as well? Thanks.

Not sure what you mean by "cooking off", but if you mean the boil, water is critical for this. YOu may or may not be able to use tap water-depends on what is in it. Same goes for well water-some works and some does not work. DIstilled water is the surest bet.

Thanks Marc,I was a bit worried about introducing another chemical so distilled is probably the way to go.Cheers.

FWIW I've had prety good service from reverse osmosis water from dispensers in my area. It's about 1/4 the cost of distilled and I go through a lot of water when I do a whole gun.

triggertate,i'll make sure it's RO.With any luck it'll be cheaper than pure.Thanks.

Use distilled water for both the formulation of the solution and for boil out...

Distilled is probably best, but rainwater will work well for the frugal man with a large enough barrel............DJ

rain will work in a lot of places, but acid rain and other chemicals hoses you up. I have heard of it happening, so you have to test your rain in your area. Condensation off of an AC works well if you take precautions to keep it clean. I know a guy who does a lot of rust bluing and he uses an RO unit as mentioned above.

Thanks fella's;i'll use RO so if it doesn't blue like I want it to i'll know exactly what my formula has got in it and can adjust it to suit.

How much do you need to do the job? I just walked into this thread and am not up to speed on bluing, but it seems to me that if you don't need 300 gallons of excellent water, you could buy an on-the-tap water purifier and save the water in some kind of jug(s) that would protect its purity until you needed it or just buy a couple of 5-gallon plastic carboys and get them filled at one of those self-serve refill where places you pay about 25 cents per gallon for it and go 'head on. I use one of the screw-on filters on my tap at home and the water is good enough for making beer, so maybe it's good enough for bluing?

Marc,

I use an old pharmacy still to make my own and put it in a 50 gallon plastic drum. The RO units work well and the cost is only in the $100 range. You can eat up that much in distilled water fast. Faucet attachments are basically worthless for what you need to create.

To follow up on what Customstox said, I have a typical $100 home RO unit under the sink that makes good enough water but since I use about 8-12 gallons per gun minimum I buy it in a kiosk dispenser because the home unit is too slow for that much volume. Its about a quarter a gallon. I change water after every second boil unless the parts are small, then 4 times max before changing. Otherwise I get buildup of acid in the water that has to be killed on the last boil with baking soda or something. Rinsing just doesn't seem to remove it well enough. Or worse yet, you finish the last parts thinking there wasn't enough rusting solution on the parts after carding, wipe them down with a good oil only to find a bunch of rusted parts in the morning from the residual acid.
One last little trick I just learned. Since I live in a giant sweat box called Southeast Texas I never built a smll one for rusting. The garage works just fine. All this cold dry weather screws that up so I rust blue when the wife is drying clothes. Just set the parts under the dryer vent oustide and one load of towels will get things going pretty good.