This is for founders who are about to buy bottles and caps for a product that will be hot filled: a sauce, a dressing, a juice, a tea. The short answer is that three numbers have to line up: the temperature your product is filled at, the highest temperature your bottle is rated for, and the temperature range your cap is made for. Then check that the neck finish fits the cap and the co-packer's line, that the cap holds through the inversion and hold, and that the label survives the heat. Those are the five checks below, and all of them can be done on paper and in a small line test before you order thousands of anything.
Settle them early. A bottle that softens or a cap that will not seal shows up on the line, after the packaging is paid for.
Why hot fill is hard on packaging
In a hot fill, the product goes into the container hot, the cap goes on, and the heat of the product treats the inside of the container and the cap. TricorBraun, a packaging supplier, describes filling "about 180° to 185° F (82° to 85° C)" and capping right away. A Kansas State University fact sheet on the hot-fill-hold method describes heating acid and acidified foods "above 180°F (82°C) or a combination of temperature and time as recommended by a Process Authority."
Ordinary PET bottles are not built for that. Pretium Packaging lists hot-fill PET for products that need a filling temperature above the 55 degrees Celsius (131 degrees Fahrenheit) "that standard PET bottles can typically accommodate." That is why hot-fill bottles are their own product line, and why the same bottle shape in a standard grade can fail.
Check 1: the bottle's heat rating, from its own spec sheet
Here is what four company pages published about heat, as we read them on October 21, 2026:
| Container | Heat rating or limit, in the company's words | Source |
|---|---|---|
| Hot-fill PET bottle, 10 and 16 oz rounds | "Hot fill rated up to 185°F" | U.S. Plastic Corp. product page |
| Hot-fill PET bottles | "Up to 185° F / 85° C" | Pretium Packaging |
| Heat-set PET, in general | "up to 185°F (85°C)", depending on the heat treatment | TricorBraun |
| Polypropylene (PP), in general | "typically extends up to 165°F (73.9°C)" | TricorBraun |
| Polypropylene, in general | a limit of 165°F, while "treated PP can be rated for temperatures as high as 205°F" | CTM Labeling Systems |
| Glass | "can endure extremely high temperatures without distorting" | TricorBraun |
Look at the polypropylene rows. TricorBraun gives 165°F as the typical limit, while CTM Labeling Systems, a labeling equipment maker writing in general terms, says treated polypropylene can reach 205°F. Both can be true, because CTM writes that the maximums "vary depending on the material formulation and wall thickness." So the material name tells you very little. The number that counts is the one on the spec sheet for the exact bottle you are buying.
The Kansas State fact sheet says the same thing from the food safety side: with plastic, "it is important to know the manufacturer’s specifications for the maximum temperature the container can withstand." U.S. Plastic adds a line worth taking literally: "Product testing for individual applications is recommended before use."
Exampleif your process calls for filling at 185°F and the bottle is rated "up to 185°F", you have no margin at all. That is the case to raise with your co-packer and your bottle supplier before you order, not after.
Check 2: the cap and its liner
Caps have temperature limits too, and on a metal cap the part to check is the liner. Plastisol is a liner used in metal caps for an airtight seal, which TricorBraun says suits "food products in glass jars such as jams, jellies and pickles." The Kansas State fact sheet names "bottles with metal caps lined with plastisol" among the best container options for hot-fill-hold.
But plastisol comes in grades. A TricorBraun guide to plastisol liners describes standard plastisol as recommended "when using a hot fill and cool process with a maximum temperature of 185°F/85°C," and high heat (pasteurization grade) plastisol as made for "hot fill and pasteurize or cold fill and pasteurize processes."
The limits can also run the other way. A 38 mm lug cap from Berlin Packaging is designed for "hot fill steam application in which steam heats the jar and creates the vacuum," and its page says: "Recommended product fill temperature for this cap is >185 degrees F. Cap is NOT recommended for water bath filling." That cap is meant for fills above 185°F, while TricorBraun's standard plastisol grade tops out at 185°F. Two caps that look alike can be rated for different fill temperatures and processes.
Two more cap points:
- The University of Minnesota Extension writes that for hot-fill hold "the lid must be a single piece and designed for proper sealing," and that "standard water-bath canning lids with a ring and lid closure are not suitable and may leak."
- The bottle's rating is for the bottle. U.S. Plastic sells its hot-fill bottles with the cap sold separately, so get the cap's own spec sheet too.
Check 3: the neck finish, which has to match the cap and the line
A neck finish is the bottle's thread size and style, written like 38-400. Paramount Global explains that the first number is the outer diameter of the threads in millimeters and the second is the thread style, and that "a 38-400 neck finish will only be compatible with 38-400 caps." Kaufman Container lists the popular thread styles as 400 (one turn), 410 (one and a half turns), and 415 (two turns).
Thread style is not the only split. Berlin Packaging writes that "lug caps are not compatible with containers that feature a continuous thread (CT) finish." So a metal lug cap needs a lug-finish bottle or jar.
The finish also has to suit the co-packer's equipment. Paramount notes that the inside diameter of the neck matters for "sufficient clearance for filling tubes." Before you buy, ask the co-packer which neck finishes their filler and capper run today, and whether your size needs new change parts.
Check 4: the inversion and hold
The hot-fill-hold method in both extension guides turns the filled container over. Kansas State describes the jar being "inverted and held, allowing the hot product to come in contact with the headspace and inner surface of the cap or lid," and says to keep records of how long it was inverted and held and the temperature after. So the cap has to stay sealed while the bottle is upside down and hot, which is one more reason to test the exact bottle and cap pair on the real line.
How hot, how long, and whether to invert are not choices for you or the co-packer to guess. Kansas State writes that these parameters "will be verified by a process authority." For an acidified food, the FDA rule says the scheduled process "shall be established by a qualified person" (21 CFR 114.83), and it requires container checks: "Testing and examinations of containers shall occur often enough to ensure that the container suitably protects the food from leakage or contamination" (21 CFR 114.80). Our post on acidified foods and the scheduled process covers the scheduled process and the process authority's part in it. Whether your product is an acidified food is a question for your process authority or regulator.
Check 5: the label
Labels get hot too. CTM Labeling Systems writes that "hot fill containers are still warm by the time they reach your labeling station," and that as the product cools "the container will contract," so the label's adhesive and face stock must flex with it. CTM adds that "most packaging suppliers include information on changes in diameter caused by temperature shifts for their hot-fill containers." Ask your bottle supplier for that figure and give it to your label printer.
The bottle packet to send your co-packer
Send this before you place a big packaging order, and ask the co-packer to confirm each line in writing:
- Bottle spec sheet: material, maximum fill temperature, capacity, and neck finish.
- Cap spec sheet: material, liner type and grade, and the process it is rated for (hot fill and cool, or pasteurize).
- Your process: the fill temperature and hold your process authority set, or say that you do not have one yet.
- Label: face stock and adhesive, if you have chosen them.
- A sample request: ask how many bottles and caps they want for a test on their line.
And three questions to ask back: Which neck finishes does your capper run today? Will my bottle need change parts? Have you run this bottle, or one like it, at this temperature before?
Hot-fill co-packers in our directory
Of the 230 listings we have reviewed from the companies' own websites, 6 name hot fill in their processes or services (as of October 21, 2026), shown with the categories each is listed for:
- Redwood Beverage Group, California: beverages
- Specialty Bottling Group, Texas: beverages, sauces, supplements, dry mixes
- Waco Bottling Company, Texas: beverages, coffee and tea, sauces, dry mixes
- New Co-Packing, Wisconsin: beverages
- Wasatch Product Development, Utah: supplements and personal care
- Raining Rose, Iowa: personal care and several food categories
Wasatch is listed only for supplements and personal care, and Raining Rose for personal care alongside several food categories, so ask each whether its hot fill line runs food or drink like yours. The other 1,080 of our 1,310 listings come only from the USDA record and have not been read from the company's website yet, so we do not know whether they hot fill. Treat this as a starting list, not the whole picture. Browse sauce and condiment co-packers and beverage co-packers for the rest, and ask each one the questions above.
What to do next
Put your container details into a co-packer brief, where you can choose hot fill as the process, so every co-packer gets the same facts. If you would rather we find the plants for you, send a free match request with your bottle, cap, and fill temperature.
Supplier ratings and pages change. Every figure above is quoted as published on October 21, 2026; confirm the current spec sheet for your exact part before you order.
The CoPacker Index team
Sources
- Code of Federal Regulations (eCFR), 21 CFR 114.80, Processes and controls, read October 21, 2026.
- Code of Federal Regulations (eCFR), 21 CFR 114.83, Establishing scheduled processes, read October 21, 2026.
- Kansas State University Research and Extension, MF3671 Hot-Fill-Hold Process for Acid and Acidified Foods (September 2024), read October 21, 2026.
- University of Minnesota Extension, Preserving food using hot-fill hold, read October 21, 2026.
- TricorBraun, Hot Fill Packaging: A Comprehensive Guide to Process and Choices, read October 21, 2026.
- TricorBraun, What Everyone Must Know About Plastisol Liners, read October 21, 2026.
- U.S. Plastic Corp., PET Round Hot-Fill Beverage Bottles, read October 21, 2026.
- Pretium Packaging, PET Hot Fill Beverage Bottles, read October 21, 2026.
- CTM Labeling Systems, Will the Hot Filling Process Work for My Product Packaging?, read October 21, 2026.
- Berlin Packaging, 38 mm Gold Metal Lug Caps (Plastisol Liner), read October 21, 2026.
- Berlin Packaging, 58 mm Gold Metal Lug Caps (Plastisol Liner), read October 21, 2026.
- Paramount Global, Guide to Bottle Neck Finishes, Thread Sizes, and Dimensions, read October 21, 2026.
- Kaufman Container, What is a neck finish, read October 21, 2026.
- CoPacker Index directory counts (230 reviewed listings, 6 that name hot fill), from blog_numbers.py, October 21, 2026.