Well it could be the candle you are using.
Usually when i petex bases at the shop i clean it out first, and if necessary i use a cutter to widen up the cut. I then proceed to candle it, try to minimize the red/orange flame, the more blue flame the better. try to get a steady stream with it (like braze welding if you know how to weld). youd want to pile it up a bit, maybe have it a few mm over the base. Let it cool for about a minutes or two and then scrape it with a metal scraper, be slow so you dont loosen the petexed area. scrape base and then you shouldnt be able to see it. Hope that helped, any other questions just ask.