Amazing Grout Cleaner

I used to be on this everlasting quest to find a good grout cleaner. As you'll see in some of the pics, I had given up on that quest long ago and decided to let the grout just become a constant dark brown instead of the light tan it was originally. I had tried every product and concoction out there. In fact I had tried everything I could think of, short of paying a professional.
So one day I saw a pic on Pinterest of a floor with half clean grout and half really dirty grout. I wasn't sure it would work on my grout because it's not sealed but I gave it a try.

Here's the formula:

7 cups warm water
1/2 cup baking soda
1/3 cup ammonia
1/4 cup vinegar

Now this much liquid didn't even close to fit into my tiny little spray bottle and it probably won't fit in yours either, so here is the recipe halved and quartered.

Halved
3 1/2 cups water 1/4 cup baking soda
2 Tbsp + 2 tsp ammonia
2 Tbsp vinegar

Quartered
1 3/4 cup water
2 Tbsp baking soda
1 Tbsp + 1 tsp ammonia
1 Tbsp vinegar

I used the quartered version for the pics below. I also wrote the formula on a piece of paper and taped it to the bottle. Make sure never to mix bleach with ammonia, you will die or something...

Here is the method:

First mix the ingredients and give the bottle a good shake.
Spray the grout (I started with 2 tiles at a time) and let the spray sit and absorb a little into the grout. Be generous.
Grab a grout brush, scrub brush, or tile brush with a handle and scrub the grout vigorously where the spray has been sitting. Don't get it in your eyes, trust me.
Use a clean damp rag to wipe each line of grout right after you scrub it to pick up all that dirty liquid, might be handy to keep a bowl or bucket of warm water nearby because you'll want to continuously clean the rag.
Depending on the color of your tile, you may want to mop the whole thing when you're done because the baking soda may or may not leave some white residue. Personally, I mopped and towel dried the floor.

Here are the "before" pics
(Click for larger pic) After one tile Two sections
And finally, three sections
There are a few things to keep in mind when looking at these pics.

1. They're all the same 9 patch of tiles
2. The dark part of the grout in the pics is NOT wet. That's what it's gotten to in the last 4+ years. It's that dark! (and no, I'm not a dirty person, again we'll just blame it on the grout not being sealed)
3. I didn't mess with the photos in any way.
4. Also keep in mind that this 9 patch probably took me an hour. Now considering I have 700-800 square ft of tile, this is going to take some time. I'm going to look for some good grout sealer tomorrow before I do anymore.
If your grout is bad like mine and you can't (or don't want to) get on your hands and knees to scrub it, you could just spray it on and use a clean damp towel to rub off whatever came up. I guarantee that you'll still see remarkable results.

Also check out My Super Secret Freebies List