Standard laser printer toner and inkjet inks are not opaque. In other words, what is behind the ink or toner will typically show through. Darker ink or toner colors like black sometimes have enough density to be opaque and block out what is behind them. I am not sure what colors you are using in your label design.
I am not quite sure what you mean when you say that you apply the labels and they appear blotchy, but I think it may be related to whatever is behind the clear label showing through. If you have a dark background behind the clear label it will make light colors look muddy or dark in most cases. That is why it is best to use a light color background (white) against a clear label when you print using a laser or inkjet printer.
The only way that I know of to get around this issue is to have your labels professionally printed and have the label company lay down a white under print layer on the printing press. The clear labels you see on candle containers in retail stores are likely printed on a professional printing press and a layer of opaque white ink is usually laid down first and then the colors are printed over that.
Unfortunately, at OnlineLabels.com, we do not offer the ability to produce labels with white under print at this time.
Consolidated Label has an excellent video explaining this issue and they are able to produce these types of labels.
http://www.consolidatedlabel.com/videos/white-underprint-for-clear-labels/I hope this information is helpful.
Dave C.
OnlineLabels.com