any reason NOT to use black comb?

You were not looking in the right place. There are 312 peer reviewed scientific studies on toxins in honey comb. Young house bees polish or coat the cells with propolis cocoon, feces and all.

Sub-Lethal Effects of Pesticide Residues in Brood Comb on Worker Honey Bee (Apis mellifera) Development and Longevity Judy Y. Wu, Carol M. Anelli, Walter S. Sheppard Research Article | published 23 Feb 2011 | PLOS ONE 10.1371/journal.pone.0014720Views: 12,753 • Citations: 34 • Saves: 79 • Shares: 32
Multiple Routes of Pesticide Exposure for Honey Bees Living Near Agricultural Fields Christian H. Krupke, Greg J. Hunt, Brian D. Eitzer, Gladys Andino, Krispn Given Research Article | published 03 Jan 2012 | PLOS ONE 10.1371/journal.pone.0029268Views: 49,768 • Citations: 48 • Saves: 107 • Shares: 434
Pesticide Residues and Bees – A Risk Assessment Francisco Sanchez-Bayo, Koichi Goka Research Article | published 09 Apr 2014 | PLOS ONE 10.1371/journal.pone.0094482Views: 2,843 • Citations: None • Saves: 9 • Shares: 53
Four Common Pesticides, Their Mixtures and a Formulation Solvent in the Hive Environment Have High Oral Toxicity to Honey Bee Larvae Wanyi Zhu, Daniel R. Schmehl, Christopher A. Mullin, James L. Frazier Research Article | published 08 Jan 2014 | PLOS ONE 10.1371/journal.pone.0077547Views: 5,514 • Citations: 1 • Saves: 16 • Shares: 64
Crop Pollination Exposes Honey Bees to Pesticides Which Alters Their Susceptibility to the Gut Pathogen Nosema ceranae Jeffery S. Pettis, Elinor M. Lichtenberg, Michael Andree, Jennie Stitzinger, Robyn Rose, Dennis vanEngelsdorp Research Article | published 24 Jul 2013 | PLOS ONE 10.1371/journal.pone.0070182Views: 132,921 • Citations: 9 • Saves: 173 • Shares: 2222
Evaluation of the Distribution and Impacts of Parasites, Pathogens, and Pesticides on Honey Bee (Apis mellifera) Populations in East Africa Elliud Muli, Harland Patch, Maryann Frazier, James Frazier, Baldwyn Torto, Tracey Baumgarten, Joseph Kilonzo, James Ng'ang'a Kimani, Fiona Mumoki, Daniel Masiga, James Tumlinson, Christina Grozinger Research Article | published 16 Apr 2014 | PLOS ONE 10.1371/journal.pone.0094459Views: 2,270 • Citations: None • Saves: 11 • Shares: 18
Winter Survival of Individual Honey Bees and Honey Bee Colonies Depends on Level of Varroa destructor Infestation Coby van Dooremalen, Lonne Gerritsen, Bram Cornelissen, Jozef J. M. van der Steen, Frank van Langevelde, Tjeerd Blacquière Research Article | published 27 Apr 2012 | PLOS ONE 10.1371/journal.pone.0036285Views: 3,957 • Citations: 9 • Saves: 23 • Shares: 16
Using a Hazard Quotient to Evaluate Pesticide Residues Detected in Pollen Trapped from Honey Bees (Apis mellifera) in Connecticut Kimberly A. Stoner, Brian D. Eitzer Research Article | published 15 Oct 2013 | PLOS ONE 10.1371/journal.pone.0077550Views: 2,020 • Citations: 1 • Saves: 10 • Shares: 19
Learning Impairment in Honey Bees Caused by Agricultural Spray Adjuvants Timothy J. Ciarlo, Christopher A. Mullin, James L. Frazier, Daniel R. Schmehl Research Article | published 16 Jul 2012 | PLOS ONE 10.1371/journal.pone.0040848Views: 5,874 • Citations: 9 • Saves: 34 • Shares: 62
Acaricide, Fungicide and Drug Interactions in Honey Bees (Apis mellifera) Reed M. Johnson, Lizette Dahlgren, Blair D. Siegfried, Marion D. Ellis Research Article | published 29 Jan 2013 | PLOS ONE 10.1371/journal.pone.0054092Views: 7,669 • Citations: 14 • Saves: 40 • Shares: 39
Cocaine Tolerance in Honey Bees Eirik Søvik, Jennifer L. Cornish, Andrew B. Barron Research Article | published 31 May 2013 | PLOS ONE 10.1371/journal.pone.0064920Views: 3,014 • Citations: 1 • Saves: 8 • Shares: 42
Gut Pathology and Responses to the Microsporidium Nosema ceranae in the Honey Bee Apis mellifera Claudia Dussaubat, Jean-Luc Brunet, Mariano Higes, John K. Colbourne, Jacqueline Lopez, Jeong-Hyeon Choi, Raquel Martín-Hernández, Cristina Botías, Marianne Cousin, Cynthia McDonnell, Marc Bonnet, Luc P. Belzunces, Robin F. A. Moritz, Yves Le Conte, Cédric Alaux Research Article | published 18 May 2012 | PLOS ONE 10.1371/journal.pone.0037017Views: 6,395 • Citations: 17 • Saves: 43 • Shares: 21
High Levels of Miticides and Agrochemicals in North American Apiaries: Implications for Honey Bee Health Christopher A. Mullin, Maryann Frazier, James L. Frazier, Sara Ashcraft, Roger Simonds, Dennis vanEngelsdorp, Jeffery S. Pettis Research Article | published 19 Mar 2010 | PLOS ONE 10.1371/journal.pone.0009754Views: 48,656 • Citations: 148 • Saves: 135 • Shares: 202
Killing Them with Kindness? In-Hive Medications May Inhibit Xenobiotic Efflux Transporters and Endanger Honey Bees David J. Hawthorne, Galen P. Dively Research Article | published 02 Nov 2011 | PLOS ONE 10.1371/journal.pone.0026796Views: 8,831 • Citations: 13 • Saves: 42 • Shares: 30
Xenobiotic Effects on Intestinal Stem Cell Proliferation in Adult Honey Bee (Apis mellifera L) Workers Cordelia Forkpah, Luke R. Dixon, Susan E. Fahrbach, Olav Rueppell Research Article | published 07 Mar 2014 | PLOS ONE 10.1371/journal.pone.0091180

In theory the cells get smaller and smaller. But the sides do not get much smaller strangely enough, it's more build up from the bottom.

The first outfit I worked for had combs that were 40 + years old, and we knew this because there had been a design change in the frames at that time. However the end bars were 35 mm wide, where the bees only need 32, so there was room for the comb midriff to get a bit wider. We also only ran 9 combs per brood box so as propolis built up on the end bars the old combs were spaced a bit wider than 35 mms.

Each spring we would pull combs from the brood nest that were no longer serviceable, they got melted, and looking at the slumgum it was surprising how thick some of those cocoons had built up at the base.

As to chemical build up, we never worried about it, however that was in the days before neonics, mites, or treatments. Wax will readily absorb many pesticides because it's wax, and many pesticides are designed to penetrate the oils in an insect. However the extent of this would depend what chemicals your bees are exposed to. If the environment around your hives is not treated with a lot of insecticides, and you do not use residual mite treatments, then you will get a lot less chemical build up than somebody whose bees are exposed to a lot of insecticides. An experiment done somewhere, may not apply to you.

I rather suspect a lot of comb is destroyed unnecessarily in the belief it is harbouring nasties that will hurt the bees when in fact levels would be too low to cause an issue. This can happen when something goes wrong with someone's hive that he cannot explain, so assumes it is down to old comb & destroys it, when the problem may lie elsewhere.

Coumaphos, and the synthetic pyrethroid ones, which are Apistan and Bayvarol.

Formic acid is not an issue for long term residue, it is volatile and evaporates out of the hive fairly quickly. Oxalic acid and thymol products stay in the hive a bit longer, but should not be regarded as residual enough to cause problems cos they will normally be down close to natural levels within several months. Apivar strips use a synthetic poison called Amitraz, however this is not regarded as residual because it breaks down once out of the strip and exposed to air, having a 1/2 life of only a few days.

So in terms of long term harmful residue in wax, the three mite treatments to worry about are Coumaphos, Bayvarol, and Apistan.

Coumaphos has some fairly detrimental consequences, Bayvarol and Apistan while residual in wax long term, have not been shown to cause much harm just by being a residue in wax at average levels, although some harm is suspected. Personally I do not use any of those three, just to keep things clean.

I actually let the bees tell me if the comb is good or not.

My first two years, I had some old comb the bees avoided like the plague. I also had some old blackish comb I couldn't get them off of, it was highly used and always full of brood. Their favorite combs it seemed. Those frames were from different apiaries, and likely had some exposures. I got rid of all of the frames they avoided and use the apparently clean, but old comb in my swarm traps. Now every frame is newer and drawn out here at my place, where I know what it has and has not been exposed to.
Yes, I gave up some of my first few honey crops to get new frames drawn. Now, I have over 4000 frames that look just like this. New drawn frames were more importaint to me than quick cash from a honey crop. Gave me a good start and I don't have to wonder about them. In the long run, I know I'm better off.

In my opinion, Knowing you have clean frames is as importaint as knowing the background of your queens. If you don't know for sure, you are risking everything.

Dirty comb may not kill your hive, but the low grade chronic exposure to brood can suck the vigor right out of it.





These are frames with half sheets of rite cell. I alternate them with full sheets until they get drawn.I get reliable worker sized cells in the center and cut comb harvest from the sides.





Early in the spring I get the drone production I want for queen rearing



You'll notice I get no messy drone cells built on the top or sides of the frame. And if I'm making up nucs and don't want all those drones, I just take my hive tool and hack them out. Foundationless part is rebuilt in a snap. WIth newly mated queens, the colony will build worker cells in the foundationless area. With an overwintered queen, they will build drone cells, them fill the cells with honey as the drones hatch and the summer progresses.

I've also found they do not backfill the brood cells with these large cells so available on the same frame.