Bubbles typically exist because wax has been poured too quickly.  When pouring wax, pour gently and then tap the sides of the mold or container.  This will likley release the trapped air bubbles.   Bubbles may also exist when too much mold release or scented oil additives are used.

The tops of candles typically collapse inward becasue wax contracts as the candle cools.  This sort of "sucks" the top of the candle inward.  To avoid this, poke a few holes about 1-2 inches deep surrounding the wick.   This will allow the air to be released from the candle as the wax contracts.  Allow to cool, then do a repour to fill in the holes.   You may need to do more than one repour. 

Several reasons could exist for this occurance:

• There may be a draft where you are burning the candle - try a different location.
• The wick may be too tall, melting too much wax - try trimming the wick.
• The wick may be too large for the wax formula - try a smaller wick
• The wick may be too close to an edge of the candle, causing wax to pool close to an edge, eventually running down a side.

This occurance typically occurs for one of two reasons.  Either:  

• Your wick is too small - this causes the flame to consume less wax at a slower rate than it is melting.  Try a bigger wick.
• Your wax is too soft - this causes the same problem as above, but the reason is the wax melts easier than it should for the wick type.   You could try a harder wax or use additives such as stearic or vybar.

This is another common problem where the wax and wick combination are not properly matched.   In this scenario, either the wick is too large for the wax or the wax is too hard for the wick size.   The wick may be burning too much wax too fast.  The easiest way to fix this is to try a smaller wick.  Alternatively, you could try a softer wax formula.   

This is another common problem where the wax and wick combination are not properly matched.   In this scenario, either the wick is too large for the wax or the wax is too hard for the wick size.   The wick may be burning too much wax too fast.  The easiest way to fix this is to try a smaller wick.  Alternatively, you could try a softer wax formula.