How to read a tested recipe
Sources last opened 2026-08-26.
The short version
A tested recipe is not a good recipe by a careful person. It is a laboratory result written down, and it always names the same set of things: the food, the jar size, the style of pack, the headspace, the canner, the process time and pressure, and the adjustment for your altitude.
If any one of those is missing, what you have is a recipe. It may produce lovely food. It is not a process, and nothing in it tells you that the heat reached the centre of the jar.
The most useful habit you can build is reading the top and bottom of a recipe before the ingredient list: where it came from, and what it says about elevation.
The anatomy
Open any procedure on the NCHFP site and you will find the same parts in the same order. Once you can see the parts, a page that is missing one becomes obvious immediately.
The food, described precisely. Not "tomatoes" but crushed tomatoes packed in their own juice. Density and pack style change how heat moves, so they are part of the specification.
The jar size. A process time belongs to a food in a particular jar. Changing the jar changes the process [F-3.10].
The style of pack. Raw pack or hot pack. Hot-packed food starts warmer and settles, which changes both the fill and the heating.
The headspace. A specific figure, given in the procedure, and different across product types [F-2.7].
The canner. Boiling water, pressure, or in some procedures a choice of both.
The process time, and for pressure, the pressure. Given as a table, by jar size and by altitude band.
The altitude adjustment. Either a column in the table or a separate instruction.
A source. The publisher, and ideally a date.
If a page gives you eight of eight, you are reading a tested process. If it gives you five, you are reading somebody's kitchen notes, and no amount of confidence in the writing changes that.
Read the altitude line before the ingredients
This is the part that catches careful people, because it is the one variable that lives outside the recipe entirely.
The USDA guide will not publish a table of elevations, and it explains why. It says it is "not practical to include a list of altitudes in this guide, since there is wide variation within a State and even a county", gives Kansas at 75 ft to 4,039 ft and Colorado at 3,000 to 10,000 ft as its examples, and warns that county-level altitudes "may actually be misleading" [F-4.5].
I find that refusal reassuring rather than unhelpful. A document that publishes only what it can stand behind is a document you can rely on elsewhere. NCHFP now runs a "Find Your Elevation" page for exactly this purpose, linked below, and finding your figure is a five-minute job you do once.
"Tested" is doing several different jobs on the internet
The word appears on pages that mean quite different things by it, and none of them are lying.
Research tested is the laboratory sense: measured heat penetration into a filled jar, pH testing, published methods [F-15.1]. This is what NCHFP and USDA mean.
Manufacturer validated means a company ran its own process and is confident in it. That may be excellent work. What it is not is work you or Extension can inspect, and the researchers quoted above were careful to say that they cannot vouch for what they have not seen [F-15.1].
Tried and true means it has been made many times without an incident anyone noticed. That is genuinely reassuring about flavour and genuinely uninformative about heat penetration, because under-processing rarely announces itself.
None of this requires you to distrust everything that is not USDA. It requires you to know which kind of "tested" you are holding, so that when two recipes disagree you can tell which one has data behind the disagreement.
Two things a recipe cannot tell you
Whether the jar worked. The recipe describes a process. Whether the process happened correctly in your kitchen — a full boil maintained, the pressure held, the vent done — is a separate question with its own evidence, and a formed seal is not that evidence. A seal shows a vacuum formed. It does not show the temperature the food reached.
Whether the food is one of the ones with no tested process at all. Some foods have no published procedure anywhere, and a recipe for them exists on the internet in exactly the same shape as a tested one. The absence of a process is not visible from inside a page that is confidently written. That is what the tested sources are for: not to check the number, but to check that the number exists.
Headspace: three different figures, and they are not interchangeable
Directions for canning specify leaving 1/4-inch for jams and jellies, 1/2-inch for fruits and tomatoes to be processed in boiling water, and from 1- to 1-1/4-inches in low acid foods to be processed in a pressure canner.
USDA Complete Guide to Home Canning, 2015 revision, p. 1-13
The link above opens the document itself, so a printed page number leads somewhere. What this document is, and who maintains it.
Opened and read by this site on 2026-08-26.
Headspace is the gap between the food and the underside of the lid, and the figure changes with what is in the jar and which canner it is going into [F-2.7].
The gap is not spare room. It is where the air is driven out from during processing, and it is what allows the vacuum to form as the jar cools. Too little and the contents push out past the sealing surface, which leaves food on the rim and gives you a failed seal. Too much and there is more air to drive out than the process was designed to clear.
The practical consequence for reading a recipe: a headspace figure belongs to that recipe. It is not a house style you can carry from the last thing you made. When a recipe gives a headspace that does not match the pattern above, that is worth a second look at where the recipe came from — not because the pattern is a rule, but because a tested procedure and its headspace are developed together.
The only jar substitution the guide licenses
Process times for 1/2-pint and pint jars are the same, as are times for 1-1/2 pint and quart jars.
USDA Complete Guide to Home Canning, 2015 revision, p. 1-23
The link above opens the document itself, so a printed page number leads somewhere. What this document is, and who maintains it.
Opened and read by this site on 2026-08-26.
One sentence, two permissions, and a great deal that it does not permit [F-3.10].
You may use the pint time for half-pints. You may use the quart time for 1-1/2 pint jars. That is the whole of it.
What it does not license is the substitution people actually want to make, which is running quarts on a pint schedule. Heat has to travel from the outside of the jar to the coldest point at its centre, and a quart jar is wider, so that journey takes longer. The time difference between pints and quarts in the published tables is not a rounding allowance; it is the extra time the centre of a wider jar needs.
Note the direction of the permission, too. It runs from the smaller jar to the larger process time, never the other way. A half-pint processed on a pint schedule gets slightly more heat than it needs. A quart processed on a pint schedule gets less than it needs.
What "research tested" actually means, from a food scientist who does it
For a recipe to meet the standards of recipes in the USDA Guide, it would need to be tested in a laboratory, often with published methods that support the data obtained as valid; this is what is 'research tested.'
I do not know that Ball is testing recipes using these standards.
The Counter, on whether Ball recipes are USDA-tested, 26 August 2021
Opened and read by this site on 2026-08-26.
Barbara Ingham is a professor of food science at the University of Wisconsin–Madison, and she led the atmospheric steam canning research that NCHFP now rests on. This is her definition, given to a reporter in August 2021.
Three parts to it. A laboratory. Published methods. Data that supports the result as valid. She added that such studies should include pH testing as well as heat penetration experiments — measuring how fast heat actually arrives at the coldest point of a filled jar.
Her second sentence is narrower than it looks, and the narrowness is the point. She does not say the best-known recipe publisher in the country tests badly. She says she does not know that it tests to those standards. That question, and what the publisher and NCHFP each said about it, has a page of its own: is a Ball recipe USDA-tested?
That is a high bar, and it is deliberately narrower than "we made this many times and nobody got ill." A method that produced a bad batch once in a thousand would look flawless in a home kitchen and fail in a laboratory, which is exactly the failure mode home testing cannot see.
In the same article, the person then acting as interim head of NCHFP said of a large commercial recipe publisher: "It is not that we do not recommend them per se, but we don't endorse them because we are not familiar with their research and testing methods." Iowa State Extension's position, given in the same piece, was not that the recipes are unsafe but that Extension cannot vouch for them. Those are careful sentences, they were said on the record, and the distinction they are drawing — cannot vouch for, as against knows to be unsafe — is one this site tries hard to keep intact everywhere.
What people ask next
The recipe is written for pints and I only have quarts.
Then you need the recipe's quart schedule, and if it does not publish one, you need a different recipe or different jars. The only jar substitutions the guide allows are half-pints on the pint time and 1-1/2 pint jars on the quart time [F-3.10]. Scaling a pint time up to a quart by guessing is the most common way a competent cook under-processes a jar.
The recipe says nothing about altitude. Can I use it?
Treat it as written for sea level, and understand that a sea-level time is not adequate at 1,000 feet or more, because water boils cooler as you go up and a lower boiling temperature is less effective at killing bacteria [F-4.1]. A tested source will always tell you how to adjust. A recipe that never mentions elevation was either written for sea level or written by somebody who has not thought about it, and you cannot tell which. Start with your altitude.
How much of a recipe am I allowed to change?
Less than you would like, and the guide is specific about where the fences are. In pickling it says outright: do not alter vinegar, food or water proportions, and do not use vinegar of unknown acidity [F-2.9]. Salt may be reduced or left out of quick pickles at some cost to quality, but it must not be cut back in fermented sauerkraut or brined pickles, where it is vital to safety [F-2.10]. Preparation steps are part of the process too — for tomatoes, acidification is still required even when you choose the pressure option [F-5.2]. Seasonings that do not change the acid, the density or the fill are the usual safe latitude.
Where do I get tested recipes?
NCHFP publishes them free and organised by food, and it is the body that maintains the USDA guide. Your state's land-grant Extension service publishes more, often for local produce. Both are linked below. That is also where the process times live, which is why this site does not reproduce them.
A page says its recipes are 'tested'. Tested by whom?
That is the right question, and the honest answer is often that you cannot tell from the page. Ask what the word is standing in for: a laboratory result with published methods, or a manufacturer's internal validation, or a family's long experience. All three get called tested. Only the first is what the tested sources mean by it [F-15.1].
Read these yourself
NCHFP — How do I can?
nchfp.uga.edu
USDA Complete Guide to Home Canning, 2015 revision
nchfp.uga.edu
The Counter — Can canners still trust the Ball Blue Book?
thecounter.org
NCHFP — Find your elevation
nchfp.uga.edu