Although officially Square Enix has never acknowledged that facing certain directions during synths affects the results, most players will agree that there does appear to be enough evidence to support this theory.
A great resource for crafting directions with moon phase and crystal type is lokyst's FFXI Crafting Timer. This page has crafting directions and even factors in the moon phase and current Vana'diel day (ie Firesday, Earthday, Lightday, etc...) for your chance of synthesizing success or hq's and skill ups.
Generally speaking though, facing the crystal's elemental direction during synth seems to increase the chance for successfully synthing an item. It also seems to make the Synth a touch easier as well. For example a Fire Crystal's elemt is Fire (Duh =P) and elemental Direction is North West. Facing a crystals elemental weakness however seems to increase the chance for a skill up or HQ synth. This also seems to have the added effect of making the synth just a little more difficult. Using the same example, Fire's elemental weakness is water and water's elemental direction is West. Facing this direction would make Fire Crystal Synths a little harder.
Of course as stated earlier, moon phase seems to have an effect as well. More crafting successes seem to happen when the moon is closer to 100% and conversely more HQ's and skill ups seem to happen as the moon gets closer to 0%. The next factor seems to be the day in which you're crafting. Using an earth crystal on it's elemental day, Earthday, seems to make synths easier as well. Using a Earth Crystal on Windsday (Wind being Earth's elemental weakness) seems to make the synth harder. putting all these factors together one can make a synth harder of easier to suit what they are trying to do. if I was using a Fire Crystal on Firesday facing North West dueing a Full Moon (100%) chances are the synth is going to be pretty successful and baring that I am not 7+ levels away from the crafts skill cap for the particular item I am trying to make it shouldn't fail either. On the other hand, Using an Earth Crystal on Windsday facing South West during a New Moon (0%) I should expect a lot of fails but during this way I would be trying for either some major skill ups or HQ items.
Either way you decide to accomplish your crafts Using a mix of all the various elements can tailor your crafting experience the way you want so play around with the elements and see where it takes you.
--Shiva.chimera 13:37, 18 May 2009 (UTC)