How long does seam sealer take to dry?

Seam sealer takes between 2 and 12 hours to cure enough to pack, depending on its chemistry: about 2 hours for a water-based urethane, 8 to 12 hours for a solvent urethane, and 3 to 12 hours for silicone, which is the one that varies most. Hardware-store silicone used in home-made mixes quotes 24 hours for a full cure. If the shelter can stay pitched overnight in the warm and dry, every common seam sealer will be ready by morning.

Seam sealer cure times by type#

Every figure below is the maker's own. Products are named because their spec sheets are the evidence, not as recommendations.

Two things stand out. Urethanes have one answer per product. Silicone has four answers from four sources, ranging from 3 hours to two days.

Which seam sealer does your tent need?#

Before timing anything, check that the sealer can bond at all. GEAR AID's urethane products all carry the same note: they "will not work on silicone-treated fabrics or sil-nylon". Its silicone sealer "will only work on silicone-treated fabrics or sil-nylon", because "silicone will only adhere to silicone".

Check the fabric on the maker's spec sheet: sil/sil needs silicone, and only a PU face takes a urethane. The silnylon vs silpoly guide covers the sil/sil, sil/PU and sil/PE distinction in detail. Most tents with factory-taped seams need no sealing at all until the tape lifts, as waterproof ratings explained notes.

Why do the silicone figures disagree?#

Silicone sealants of this kind cure by reacting with moisture from the air, starting at the surface. GE's data sheet for its all-purpose silicone says the cure rate "is primarily dependent upon temperature and the availability of atmospheric moisture", and that at 23 degrees C and 50 percent humidity the sealant "can attain a cured thickness of 2-3 mm per 24 hours". It also warns that in a confined space the sealant "will cure only from that surface which has access to the atmosphere".

So time depends on depth. A thin brushed film cures in hours. A bead pushed into a seam, or sealant pooled where three panels meet, takes longer, and the skin on top says nothing about the core.

The makers also measure different things. GEAR AID's 3 to 6 hours is a spec-sheet cure figure and Tarptent says "dry". Six Moon Designs is telling customers when to take a shelter down, and allows two days in its own workshop because "cold, humid winter weather may take longer".

How thick is the coat you are curing? The arithmetic#

GEAR AID's coverage figures can be turned into a film thickness: the volume in the tube spread over the area it claims to cover. Fluid ounces are converted at 29.57 mL. For the two tubes sold by weight, we take the density as about 1 gram per mL. Permatex lists 1.05 for its silicone, so that assumption is close for silicone and approximate for the urethane.

Now put the silicone figure against GE's cure rate. At 2 to 3 mm per 24 hours, a 0.9 mm film takes 0.9 / 3 x 24 = 7.2 hours to 0.9 / 2 x 24 = 10.8 hours to cure through. That is Six Moon Designs' 8 to 12 hours almost exactly. GEAR AID's 3 to 6 hours corresponds, at the same rate, to a film of 0.25 to 0.75 mm: a thinner coat than its own coverage figure implies.

Thinning changes the answer. Six Moon Designs' home-made sealer is silicone caulk and mineral spirits "equal parts by weight". Once the spirits evaporate, a brushed coat of the same wet thickness leaves about half the silicone, roughly 0.45 mm, which the same rate cures in about 3.6 to 5.4 hours. Tarptent's "3-4 hours" for its pre-mixed solution sits at the fast end of that range.

The urethanes behave differently. FC and TF are water-based and dry as their water evaporates. WP's spec is the only one with a humidity floor, "above 40% relative humidity", and the longest seam time, 8 to 12 hours.

How temperature and humidity change the time#

All four GEAR AID sealants list the same application temperature: 60 to 100 degrees F, which is 16 to 38 degrees C. Below that, GEAR AID gives no cure time at all: the range is simply where it says to apply its sealants.

GE's data sheet is more specific about silicone. Its times are for 23 degrees C (73 F) and 50 percent relative humidity, and "cure time is significantly increased in cold temperatures and/or low humidity conditions". The sealant must not be applied below 0 degrees C, and "for standard cure speed" should go on above 4 degrees C (40 F). GE recommends 21 degrees C (70 F) for best performance.

Warm, humid air puts silicone at the fast end of every range above. Cold air slows every sealer here, and dry air slows silicone. On a cool or damp day, seal indoors.

When can you pack a tent after seam sealing?#

The packing time is later than the "dry" time, because a folded tent presses sealer against fabric under pressure, with no air reaching it.

• Seam Grip WP: the insert is explicit: "Allow Seam Grip + WP to cure for 8 to 12 hours before packing tent."
• Silicone, bought or mixed: overnight at room temperature, pitched. Six Moon Designs says to leave the shelter pitched for 8 to 12 hours; Gossamer Gear dries overnight. If it is still tacky when you need to bring it in, Tarptent's advice is to take it down and throw it over a chair for the night, not to fold it.
• Seam Grip FC: the maker gives 2 hours. Leaving it longer costs nothing.
• A TF fabric recoat: GEAR AID's how-to says "test dryness after four hours and wait 24 hours before storing". This is the slowest step in the strip and recoat procedure for a sticky fly, and it is a whole panel of coating, not a seam line.

Before long-term storage, give any sealer GEAR AID's 24 hours: a tent folded into a cupboard stays folded for months. The gear storage guide explains why it must also go in bone dry.

Can seam sealer get wet before it cures?#

GE's data sheet is the only source here with a figure. Its silicone can take water after 12 hours, but only with a bead no thicker than 6.3 mm, at 18.3 degrees C (65 F) or warmer and at 50 percent humidity or more. "Otherwise, sealant should not be exposed to water for 24 hours." None of the tent makers gives a rain figure, so the cure times in the first table are the only guide for their products.

The safe plan is to seal at least one full day before you leave, test with a hose the next morning, and touch up any spot that leaks. Six Moon Designs says to mist the shelter with a garden hose "mimicking rain from various angles", let any leaking spot dry, recoat it and test again. Tarptent describes the same check. A recoated spot needs its own cure time before the trip, so a leak found the night before departure is a leak you take with you.

Test it yourself: is the sealer cured?#

A fingertip only tells you whether the surface has skinned. To check the core:

1. Make a witness sample. When you seal, brush one stroke of the same sealer, at the same thickness, onto a piece of kitchen foil or a plastic lid. Leave it beside the tent so it cures in the same air.
2. Check the surface on the seam. Touch a seam lightly with a clean fingertip. If anything transfers, it is not ready.
3. Peel the witness. When the sample on the foil lifts off as one elastic film with no wet or stringy layer underneath, a seam coat of the same thickness has cured through. A soft core means wait longer.
4. Check the thick spots. Pooled sealer at seam junctions, corners and tie-out patches is the last to cure. Press each one with a fingernail. It should spring back, not dent.
5. Hose test. With the shelter pitched, mist it from several angles for a few minutes and check every seam from inside. Damp fabric after a cold night is more often condensation than a seam, so test in daylight.
6. Powder the residual tack. A slight tack after cure is normal: GEAR AID's WP insert says it "will dissipate with tent use". Dust it once cure is confirmed, not before.

On powder: GEAR AID's current WP insert specifies "talc-free powder", although its 2020 how-to said "talcum powder". Six Moon Designs suggests unscented talcum powder and Gossamer Gear uses baby powder, wiping off the excess after about 30 minutes with a damp rag. Any fine, unscented powder does the job.

Common mistakes#

Sealing in the evening and packing in the morning when it was cold overnight. Below 16 degrees C (60 F) the time on the packaging no longer applies. Bring the tent indoors, or give it another day.

Laying the bead on thick to be safe. Silicone cures from the surface inward, so a thick bead takes several times longer to cure through, and it may still be soft inside when the surface feels dry. Thin coats, worked into the stitching, and a second coat if the hose test asks for one.

Folding a fabric that has just been recoated. A TF recoat covers a whole panel. GEAR AID's own guidance is 24 hours before storing.

Leaving a part-used tube in a warm drawer. GEAR AID says to keep a part-used WP tube "in a plastic storage bag in the freezer", but lists the water-based FC and TF as not freeze-thaw stable: cool, not frozen. Check it with the rest of the field repair kit before the season.

Frequently asked questions#

How long does Seam Grip take to dry?#

It depends which Seam Grip. GEAR AID gives 8 to 12 hours for Seam Grip WP, the urethane in a tube, and says to wait that long before packing a tent. Seam Grip FC, the water-based brush-on version, is 2 hours. Seam Grip SIL, the silicone one for silnylon, is 3 to 6 hours. All three assume 16 to 38 degrees C (60 to 100 F), and cold slows them.

How long does SilNet take to cure?#

SilNet is now sold as Seam Grip SIL, and GEAR AID lists its cure time as 3 to 6 hours. Shelter makers that use it advise longer: Six Moon Designs says to leave a shelter pitched for 8 to 12 hours, and allows two days in its own sealing workshop. A thin brushed coat in warm, humid air is at the fast end. A thick bead on a cool day takes longer.

How long should DIY silicone seam sealer dry?#

Overnight, pitched, in the warm. A mix of silicone caulk and mineral spirits leaves a thinner silicone film than undiluted sealer, so it cures faster: Tarptent says its pre-mixed solution takes 3 to 4 hours to dry depending on conditions. The hardware-store caulk itself quotes 24 hours to full cure at 23 degrees C and 50 percent humidity. Check a witness strip on foil before packing.

Can I seam seal a tent in cold weather?#

Not well. GEAR AID lists 16 degrees C (60 F) as the minimum application temperature for all its seam sealers. GE's silicone data sheet says cure time is significantly increased in cold and dry conditions, and forbids application below freezing. Seal indoors, in a heated garage or a large room, and leave the tent there until a witness sample peels off cured.

Do I seal the inside or the outside of the seams?#

Follow the shelter maker. GEAR AID's tent instructions put Seam Grip WP on the inside. Six Moon Designs says its shelters "need to be sealed from the outside", whatever the sealer packaging says, because their butt seams have the thread on the inside. Gossamer Gear passes on a user's tip of pitching a tarp inside out to seal it from the inside. The cure times are the same either way.

How long after seam sealing can a tent get rained on?#

None of the tent sealer makers gives a rain figure, so treat their cure time as the minimum: 2 hours for a water-based urethane, 8 to 12 for solvent urethane, overnight for silicone. GE's data sheet allows its silicone to get wet after 12 hours, but only above 18 degrees C and 50 percent humidity. Otherwise it says wait 24 hours.