Your Sound - Bow Speed - Bow Placement - Timbre - Arm Weight
The bow has a certain amount of weight and because the weight is unevenly distributed, it takes the coordination of many muscle groups to be able to play in a relaxed manner with good tone.
Important concept: The fingers do not exert pressure, they only transmit weight into the bow. Your right arm, the bow arm needs to learn how to release muscle tension as it moves and balances through a stroke. It helps to imagine that you are releasing weight downwards towards the floor. Beginners sometimes think you should press the bow inwards towards your body. NO! It may look that way in paintings and photos but that sensation is not what you are after.
There is a downward force on the string from the weight of the bow and from your muscles, but don't think of it as force or pressure. Please go to Arm Weight for clarification on this vital topic.
Never squeeze or press the string down. This deadens the vibrations of the string and will cause physical problems throughout the body.
To venture towards the bridge, you need to add weight. This is not something for beginners to contend with. It's easier for beginners to increase the bow speed to get more volume.
When you can play a legato piece with vibrato, you are ready to try playing close to the bridge. I like the image of sinking into bread dough or thick chocolate pudding. You can practice this by doing "swells"
(Video demonstrating swells)