You can just scoop up the baking powder with the end of the refill and then push it inside with a stick. Now put a tiny amount of baking powder in the refill. Put a tiny amount of water in the refill. First pull the drinking straw so that it becomes thinner at the middle. If you dont have a syringe then use a drinking straw. Now because of high surface tension the water will not go in easily.You can use a syringe to put in the water. First of all put a little bit of water into the refill. They react to produce carbon dioxide which increases the pressure inside the refill. We will put water and baking powder into the refill. They might not be as good as the nasa pen, but still can be pressurised with little or almost no leakage. Modern ball pens have a good sealed tip too. For our pen we will pressurise the refill and seal it. They tend to be expensive because of the high quality seal at the tip which prevents leaking and maintains the pressure for years. So the pen writes smoothly even against gravity.

The space pens actually contain pressurised air which pushes the ink out while writing. For your ordinary pen if you try to write against gravity then the pen will stop working soon after you begin writing. You can simply convert any of your standard ball point pens into a space pen. But now you dont need to hurt your wallet to get one. There are also some other brands which are expensive as well. Nasa and a company called fisher have developed a space pen that is commercially available. Anti gravity pens or space pens are really interesting because of their capability to write at any angle in zero gravity or against gravity.

Support against gravity circuit