Hi, I am looking to become a amateur pyro tech and I wanted to mess with some flashpower mixes, but when it comes to this type of stuff, you can never be too safe. I was thinking I would use my shed but I just wanted to know what precautions I should take while making this stuff.

I was going to compleatly clean out and power wash the shed to remove most of the dust and add some humidity. Spray everything down with static guard, where anti static gloves, and instead of using the "diaper method" I was going to use a large medicine bottle (i.e. large tylenol/vitimans....) with a wodden broom handle tapped to the end so I can mix it at a distance.

Mixture:
70% Potassium Perchlorate(High Purity-Chineese) , 20%Aluminum Flake(dark German pyro grade), 10% Magnesium Flake

Sounds good. Let me know your thoughts

Try to use common sense safety precautions.
Have a large bucket of water handy to do emergency douses.
Have the garden hose primed and ready to go.
Have some sand for metal fires.
Get a real fire extinguisher.
Get a wet blanket for yourself just in case you catch on fire, or a real fire blanket.
Make sure you don’t have too many flammable items nearby when you are mixing and grinding your preparations. You may want to have an outside table set up for certain operations.
Wear eye protection!
Don’t smoke!
Wear pants, a long sleeve shirt, and rubber soled shoes. Wear no loose clothing that can snag on your chemicals or equipment and come crashing down on the floor or you.
Wear no open toed shoes (like sandals) because you may spill something on your feet.
Use wood or glass utensils, try to avoid metal if you can because of spark hazards.
Wear eye protection! Yes, this one is listed twice. If your plastic container blows up your hand should heal, but you can’t regrow eyes.
If you get nervous like I do a plastic blast shield can be comforting. I snagged one that was being thrown away (perfectly good, what a disposable society we live in), but any kind of PLASTIC barrier will at least save you some stitches even if it breaks. Don’t use glass, that will only make matters worse if flying shards are coming at you.

Megalomania pretty much said it all; common sense is your best friend.

I just want to add a few little precautions:

First of all, start out by making small quantities; just a few grams at a time. If you don't have experience in this sort of thing, you really have no idea what you're dealing with until you set off a tiny bit. So start small.

Second, keep in mind that shrapnel will travel far. Even at the distance that your wooden broom will give you, you could easily get hit by shrapnel. So if you use a bottle, I'd suggest a soft plastic bottle, not something hard like thick plastic, or, heaven forbid, glass.

Finally, be careful with friction when opening a container of explosives. Some explosives are very friction-sensitive, and getting some in the threads of a screw-jar would be very dangerous.

I agree with Megalomania and Heat for the most part... Good points heat on the shrapnel factor.

Over the past few years I have come to appreciate any and ALL compound mixes, that said it all depends on WHAT you’re mixing up... Flake AL will catch quickly when burned but you have to pay attention to what level of mesh you’re using. Anything over a 1200 mesh flake may just ignite when mixing in a bottle or with a spoon. The friction times the BIBILICAL surface area of that level of mesh can cause enough heat to cause it to ignite. That said, diaper method all the way IMHO.

The biggest thing to remember is that flash powder can be produced that is 2 to 20 times more powerful than a standard black powder. That said, all the precautions in the world won't help you if you measurements are off by a gram. That and you mix it at any speed in a bottle.

Be safe and start out small (3.5g KCIO4 and 1.5g of Al), I know you mentioned Mg but to be honest, mix up a few batches of the pure AL above, get a feel for it then start messing with Mg, mainly because the addition of Mg to most mixes increases sensitivity quite a bit and has been known to self-ignite when mixed with some oxidizers. Above all have fun and start small!!

Most of the above is good advice. Only a few things to add.

If you have german dark Al, don't bother with adding Mg powders. 70/30 will be quite enough for a first time experiment. Mg flash doesn't store well.

Mix on a humid/ foggy/rainy day to minimize static risks. Be aware that a dust cloud is a static generator. Drum mixing of flash powders such as you discuss has led to accidents when tried on an industrial scale.

Wear a dust mask at all times you have open containers of chemicals, are mixing or charging devices. Al powder that fine will makie it all the way to the alveoli and never leave your lungs.

Im going to be doing this for the first time tonight.
I've got a whole bunch of precations laid out for myself:
Anti Static spray, concrete floor, wooden table, plastic cups, natural fiber brushes, ivory soap, several kinds of glue to try, several kinds of Al both german dark and some from ebay to try and test with the KClO4.
I've even made some of my own Kraft paper cases for the stuff, and got some of the premade cardboard ones off ebay to try.
My method will be to mix no more than 10g at first, then max out at 23g if it feels safe (after I test it a few ways) should be ok since critical mass is supposedly around 50g.
Ill be sealing the salutes up first w/ glue and fusing them as well, then loading and adding one final glue to seal them up.

All of the points made by members are good common sense. Another that I
do is weigh out the ingredients with only 1 chemical container open at a
time. After the ingredients are weighed, I mix them far away from my
chemical stocks in case of an accident. I haven't had an accident as an
adult and I don't want to risk one.

Just a follow up from yesterday: Im still alive :-)
I mixed up 10g just like I said I would, and loaded 2g into 4 salutes. the last 2g was lost in dust or spill (and cleaned up of course).

I took the 4 of them out not quite knowing what to expect (using some Al from ebay, a company called "exchem" or expeditedchemical also his KClO4) I wasnt sure what to expect...
My report is that after lighting just one of the 2g salutes off, I didnt have the guts to do the other 3!! I've never experienced something like that before, it was exciting and scary, and I can see why this stuff is so dangerous.

What kind of container did you use? I normally dream of using 16" ID, 1½" lenth, and a 1/16" wall sized tube. I put 3 grams of 7:3, KClO4:Al in the tube and paper plug it. I really never know if I am going to side fuse or end fuse until I start.

When setting off larger than commercial amounts of confined flash, the report is a very amusing experience.

Well I made my own containers by dry-rolling lightweight kraft paper on wooden dowels, coating then with a good paper-acid free glue and letting dry... then cutting to appropriate lengths. Several trial and errors with this stuff, its very hard to get a tight roll and keep it together, at least for me never having done it before.

I hot glued a kraft paper end plug and put the fuse in the middle of that, with hot glue on top.
when all dry and cool, I loaded it with 2g of the flash using a paper funnel then plugged it with a flat piece of kraft paper and set it down in white-elmers glue to tack then removed it to dry sideways hanging over the table.

I have several size dowels, I used the second size up (Not in front of me right now, but probably ID dia of just under 1/2") 2g about filled it half way, I cut it kind of short.
I bought some cardboard tubes on ebay to use so I wouldnt have to make my own forever. they are pretty cheap, 50 of them for about $5 USD.

Ninja edit:
and on the topic of making them, I suppose ill share how I mixed it. I have a set wooden table on a concrete slab outside blocked on 3 sides by concret walls, so wind wasnt a problem. I put some kraft-tissue paper down on my electronic scale, and brought out the Al first and measured out exactly 3g of it on the scale. then the Al was put away and a different tissue was put on the scale and exactly 7g of KClO4 was laid on it. Then a completelly new tissue was placed between the two tissues containing the chems, all of the chems were put away in their containers inside the house by this point... I took a 30 mesh stainless screen and filters the KClO4 first down onto the new tissue to break it up and fluff it. It didnt need i IMO, it is alot like fine sand. I then did the same for the Al, filtering through the 30 mesh screen right down on top of the KClO4. this done, I gently diaper mixed the two together for 3-4 minutes until I was sure the mix was thorough. A new tissue placed on the scale measured out 2g exactly which was loaded into my salutes.

King,

Cannonfuse-dot-com

Excellent prices and supplies on tubes and VISCO fuse, have used them after getting bored of making my own shells. Happy 4th!!