First we must consider that there is no such thing as a "bad" candle. The Bible is filled with stories of God using the worst sinners to do great good, so it is not unreasonable that what we perceive as a "bad" candle is not part of God's plan and that even a poorly manufactured candle can and often does produce accurate signs.
A broken candle is typically considered a "bad" sign, however, it must be considered in relation to the type of candle that is being burned. If this candle is burned to bring some kind of increase or bring two people together it is a bad sign; if the work is for decrease, it is symbolic of a split or break to come and this often occurs in a sudden and unexpected manner. For example,
- if the candle is for money-drawing and the glass breaks, this may mean that the person for whom the candle is being burned will also be "broke" (i.e. have no money). If the break or crack results in running wax, it could augur their money running out and / or their inability to hold on to any money at all.
- if this candle is for keeping a lover such as follow-me-boy or stay-with-me, then this may be symbolic of a break or separation to come.
- if the candle was for success or achievement such as crown-of-success and the candle breaks off near the top or "crown", then this would be a bad sign.
Sometimes a break indicates that the candle took a "hit" for you in the case of a protection candle; in other cases (such as crossing or hot-footing another) it may mean that the target is protected by spells or by a strong spirit. The target may be resisting your spell and is also fighting back. If you are petitioning a spirit, a broken or cracked candle may mean that the spirit petitioned does not wish to work with you or is warning that your actions or unjustified.
In any case, a complete picture may only be obtained by closely inspecting your spent candle and considering the broken / cracked glass along with any other signs produced from burning your candle. In some cases, it may be necessary to consult your divination tool for clarification or further details.