Open Field Protocol

Bleach Dwell Time Against Feeder Biofilm

The standard clean is a scrub, then about 10 minutes in 1 part household bleach to 9 parts water, then a thorough rinse and a full dry. This protocol tests whether the 10 minutes matters, and how much of the work the scrub is doing on its own.

The question this answers#

How to clean a feeder gives one sequence: dismantle, scrub with hot soapy water, soak about 10 minutes in 1 part unscented household bleach to 9 parts water, rinse thoroughly, dry completely. The 10 minutes is the number people argue about, usually while standing over a bucket wondering whether 3 would do.

So test it. Arm A varies dwell time across 0, 2, 5, 10 and 20 minutes with an identical scrub every time. Arm B holds dwell at 10 minutes and varies the scrub across none, half and full. The outcome is visible residue on defined surfaces, scored 0 to 4 before and after cleaning by a white cloth wipe, a food-safe stain and fixed photographs.

Why the existing evidence is thin#

The 10 minute soak is a sensible convention borrowed from general disinfection practice. The laboratory work behind that practice uses smooth test coupons, controlled organic loads and colony counts, none of which describe a three year old feeder with scratched ports and a gasket groove full of seed oil. Nobody has published a home-scale comparison on real feeders, largely because the outcome that matters is invisible.

Say the limitation out loud before you start, because it shapes everything you may claim afterward. Soil removal and disinfection are different things. A surface can look spotless and still carry viable salmonella, and a stained surface can be harmless. What this protocol can compare is how much visible organic residue each treatment leaves, which is worth knowing precisely because disinfectants penetrate organic material poorly. It is evidence about the scrub, not a verdict on the soak.

What you need#

• Seven feeders of the same model and age, or one feeder run through seven rounds in randomized order.
• Unscented household bleach, a measuring jug, a tub big enough to submerge parts, and a timer.
• Gloves, splash goggles, and an outdoor tap or a utility sink.
• Bottle brush, port brush, old toothbrush, dish soap.
• White cotton cloth or coffee filters cut into squares, one per swab site.
• A food-safe stain: ordinary food coloring, or a food-grade fluorescent training gel of the kind sold for handwashing and food-safety training, plus a UV flashlight.
• A phone camera on a small tripod, one lamp in a fixed position, a white or gray card, and a printed residue swatch card.
• Tape and labels, and an assistant willing to hide them while you score.

How to set it up#

Soil the feeders identically: same yard, same rack, same seed, same 14 days. Feeders dirtied under different conditions are not comparable, and the dirtiest one must never land on the treatment you expect to win. Draw assignments at random and write them down before you start.

Define three swab sites per feeder and use only those: the inside reservoir wall about 2 in (5 cm) above the base, one port rim, and the base seam. Mark them so you return to the same spots after cleaning.

Define the full scrub as a recipe, not a feeling: about 2 quarts (2 L) of hot water near 110°F (43°C) with 1 tsp (5 ml) dish soap, 20 bottle brush strokes, 5 port brush twists per port, 15 seconds of toothbrush per seam. Half scrub halves each count. No scrub is a 15 second rinse and nothing else.

Fix the photography before the first round: camera 12 in (30 cm) from the part, one lamp in a fixed place, exposure locked, reference card in frame. A brighter photo is not a cleaner feeder.

The procedure#

1. At the end of the soiling period take every feeder down, empty it, and pre-score it dry: wipe test at the three sites, then photographs.
2. Dismantle completely, including base, perches, ports and gasket, then scrub at the assigned level, counting strokes out loud.
3. Mix 1 part bleach to 9 parts water fresh, and soak fully submerged for the assigned dwell, timed from the moment the last part goes in. The 0 minute arm gets an identical dip in plain water so handling stays constant.
4. Rinse every part under running water until there is no bleach smell, then rinse again.
5. Dry completely, parts standing open in moving air: 1 to 2 hours in warm dry conditions, most of a day in cool damp weather. Never score a damp part.
6. Post-score with the white cloth: one pass per site, moderate even pressure, a fresh cloth face each time. Score the transfer against the swatch card.
7. Then stain the same areas. Apply the dye or gel, leave it 60 seconds, rinse a fixed 10 seconds, and look, using the UV flashlight in a dark garage for fluorescent gel. Score what is retained, and photograph it with the rig.
8. Put every stained feeder through a fresh full clean, scrub, 10 minute soak, rinse and complete dry, before it goes back into service.
9. Repeat with treatment assignments re-randomized so no feeder always draws the same arm.

What you record#

One row per feeder per site per scoring event, pre and post. Score against the printed table.

Also record round, feeder identity, arm, scrub level, dwell minutes, bleach batch, water temperature, soiling days, drying hours, site scored, pre score, post score, the difference, photo names, who scored, and whether the scorer knew the treatment.

Controls, and the ways this goes wrong#

Carry one untreated feeder through each round, scored and photographed but never cleaned. It shows whether your scale has drifted between rounds, which it will.

Score blind if you possibly can. Have someone else strip the labels and hand you coded parts, or score later from photographs with the treatment hidden. Knowing that a part soaked for 20 minutes is enough to make you see less on the cloth.

Clean in randomized order, because your technique warms up and the last feeder of the evening gets a better scrub than the first. Use fresh solution per feeder, or record that you reused it, since diluted bleach weakens as it sits and as it meets organic matter.

Now the limits. This is a residue test. You may fairly report that two dwell times left visually indistinguishable residue under this scale, or that scrub level separated the scores while dwell time did not. You may not report that a shorter soak disinfects, that a feeder is safe, or that the 10 minute standard is unnecessary. Disinfection is measured by culture, and swab kits read by a laboratory are the only route to that claim from a backyard. Until someone does it, the published method stands.

How many runs before the number means anything#

Six rounds is the floor and ten is better, with every treatment applied to at least three different physical feeders. Ports scratch, plastic ages, and one feeder carries its history into every score it produces.

Report the median change from pre to post for each treatment, by site, with the spread. A one point difference on a five point ordinal scale scored by one person is weak evidence, so look for consistent ordering across rounds: does 20 minutes beat 2 minutes in most rounds, or does the ranking shuffle? A ranking that shuffles is itself a result worth publishing.

Publish the photographs alongside the numbers. Residue scoring is a judgment call, and the only way a reader can check your judgment is to look at what you looked at.

Submitting your results#

Use the datasheet for this protocol, one row per feeder per site per scoring event, and keep the pre-clean rows: half the analysis lives in them.

Send rounds through the Feeder Log with your feeder model and age, the stain you used, whether scoring was blind, and your photo set. Voided rounds are worth reporting too.