EDIT 2014/9/7: With the release of Crius, this no longer works. Do not use it.
Some items which are built with minerals have substantially smaller volumes than the minerals required to build them. Additionally, some such items can be reprocessed with essentially no loss. Combined, these features allow us to move in a single run volumes of minerals much larger than the cargo hold of the ship we are using to move them. This is especially useful when moving minerals to lowsec or null.
Step 1: Acquire compression and decompression stations.
You probably don't want to compress minerals in jita 4-4, so find a highsec station with wait times low enough that they won't be an issue.
In order to decompress minerals without loss, the station where you reprocess your compressed minerals needs to have a minimum reprocessing rate of 40%, and you may need good reprocessing skills on top of that (see "refinery efficiency" and "scrapmetal processing"). Additionally, there must be no reprocessing tax. In NPC stations this means you must have 6.67 (or thereabouts) standings with the owning corporation. In player owned stations, you will have to ask your alliance.
Step 2: Research compression blueprints.
There are various blueprints you can use for this, but their functions are pretty similar. The only major difference I have been able to find is that some blueprints (e.g. scripts, ammo) only use a few types of mineral. If you are building ships, as in this example, a gun blueprint (e.g. "425mm railgun I") will get the job done. Guns are nice because compared to ships they use vaguely similar ratios of minerals.
For serious compression, I recommend researching 10 blueprints to some relatively high level. I went with ME 262 (because that's how much I could get in a month) and PE 20 (just because). Note that it is important for all your compression blueprints to have exactly the same material level.
Step 3: Acquire your minerals.
For this post I will be using my capital production run number 110 (2 chimera, 2 thanatos, 2 archon, 2 moros) as an example. The minerals for these are worth 11 billion isk, and have a volume of 7.2 million m^3. This is equal to eight trips in a freighter, or 20-ish in a jump freighter.
- Note: There is some loss involved in mineral compression. It is very small - I measured it at one-fortieth of one percent at my material level - but it does exist. This is a nonissue for me, since I already round the third digit of my mineral quantities upward and do periodic corrections. This is easy to do, so you might be well served by doing something similar.
Step 4: Move the minerals to your building station.
I recommend using a freighter.
Step 5: F yeah, spreadsheets.
Let's face it, this is what you've all been waiting for.
Your spreadsheet needs 3 columns and one field. The first column is the quantities of the minerals you want to compress. The second column is the quantities of those same minerals which you need to build one unit of 425mm railgun I (or whatever).
The single field is equal to the quantity of tritanium you want to compress, divided by the quantity of tritanium used to build one railgun, all rounded down to the nearest whole unit. This is the number of railguns you are going to build.
The final column is equal to [quantity to compress]-([quantity per railgun]*[number of railguns].)
Click here to download the tool pictured above (open document format).
Step 6: Fill in negative values.
Some of those numbers are negative. Wat do?
Write down the numbers in red. This is important. Then, buy those precise quantities of minerals and put them in your building station with the rest. These will be recovered later.
- Note: I recommend having a station container in your building station to keep filler minerals in, so they don't get mixed up.
Step 7: Install runs.
As you see above, we have 5,139 railguns to build. This number is not evenly divisible by 10, so what we do is drop the 9, giving us 513. We add 9 to the first run, and use 513 for all the rest. This gives us 1 run of 522 and 9 runs of 513, for a total of 5,139.
(See how having 10 railgun blueprints makes things so very, very, easy?)
If you do it right, after installing all 10 runs the stacks of minerals which were in red will disappear.
Step 8: Deliver railguns.
Pretty much self explanatory. Building all these railguns from one blueprint would have taken most of a month, but by dividing them into 10 runs our production time is less than three days.
Step 9: Move minerals to decompression station.
Our left-over minerals this run came to 46k m^3, which is slightly more than normal; usually, the leftovers fit in a cloaky hauler. Still, leftovers plus railguns do fit comfortably in my jump freighter.
Note that the compressed volume is 1/23rd that of the uncompressed minerals.
Step 10: Reprocess into minerals.
Step 11: Recover excess minerals
Remember those numbers you wrote down back in step 6? This is where you use them. Split the quantities of minerals you added in order to build the railguns off from of the stacks of reprocessed minerals, and put them in your cargo. When you head back to your compression station, drop them off in the station container you have there so they can be re-used next run.