Introduction: 30 Minutes Hourglass

This is an instructable for hourglass, which will measure 30 minutes of time, so if you do morning excercises, afternoon meditation, or evening yoga  for a similar time-span, and prefer to have a non ticking, or non blinking clock, you can try this one. 

You'll need some basic tools, like drilling machine, riveting tool, or angle grinder, but it's also possible to use a primitive aproach and completely ignore nuclear energy. Materials needed:
- Two glass jars, each 3l capasity;
- Aproximately 3l of sand. Try to find finest possible grade. I used very clean and fine sand from baltic sea shore. If you put more effort, you can find or buy white, red or black sand;
- For struts I used two shovel handles. That's a cheap way to go. Custom turned struts would be another level;
- A piece of wooden board, about 2cm thick and 20 cm wide.
- A 10x10cm piece of strong enought and preferably rustproof tin-plate; 
- Brass (or copper, or gold :)) tin-plate for decoration;
- Small nails, flatheaded screws, some paint and floor vax or oil.

Step 1: Verrry Important Hole

Place a jar on a 10x10cm tin-plate upside down and draw a line around. Cut or grind away to the line. Mark the center and drill a 2mm hole. The hole diameter depends on your sand quality, so pour some dryed sand in to the jar, put a tin-plate circle with a hole on top and then another jar. Carefully turn everything upside down and see if it works. If sand doesn't flow, you have to drill bigger hole, maybe 2,5mm and try again. If you see sand falling down in a nicely shaped string, we can move on.

Step 2: Measure Twice

Take that 2cm thick board and cut two 18x18cm pieces for the base. This size may be different, depending on your jars diameter.  Look at the first picture and you'll see how to measure the height of the struts. In my case that was 47cm. Add 2cm for joint, and cut shovel handles to four parts, each 49cm long. That's it.
Now locate the jar in the middle of the base and mark the holes for the struts. Struts should stay in touch with a jar. Repeat this with another base. My struts are 3cm in diameter, so I had to use 2cm drill for the 1cm deep holes. On the struts mark a line 1cm from the ends. Use your knife and make the ends nicely fit to the holes. Put a jar in a preasembled unit and check for possible misstakes. Damn, I made them, so in order to fit a jar I had to to take away some parts of struts using knife. It was nots so easy, so better check your measurements before drilling holes.

Step 3: Hot Sands

Before sealing the sand in the unit, you have to completely dry it. I used oven for this purpose. You can use sunshine, if there is any, or even fire. Also before sealing, you have to find right amount of sand for desirable time-span. Take your time, pour sand in to the preasembled unit, carefully  turn the unit upside down and check how long it takes. Add more sand or take away some and try again. I did it three times. When testing is finished, seal the unit by wraping clear adhesive tape around the joint.

Step 4: Beauty

Ok, till this moment it was all technical things, but now you have to become an artist and use your imagination. Here important is only one point- you have somehow to cover that plastic adhessive tape. For this purpose I used wrapped around and riveted brass tin-plate, but there are hundreds of ways to go- you choose. I sanded and painted wood parts with acrilic paint and polished using floor vax. In the middle of the struts I also nailed brass tin-plate, in order to achieve some harmony in decoration.
Finaly you have to assemble everything. I didn't use any glue, but simply screwed struts to base. That was enough for sturdy and stable construction.