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🛠️ Float, fill, and silence like a pro—foam that works as hard as you do!
Fiberglass Supply Depot’s 4 lb density expanding pour foam is a two-part polyurethane closed-cell liquid foam designed for superior flotation, soundproofing, insulation, and filling voids. This quart kit mixes equal parts to produce ½ cubic foot of foam that cures in 5 minutes and can be laminated with various resins without damage. Ideal for marine, industrial, and creative applications, it offers waterproof durability and versatile performance trusted by professionals.










| ASIN | B08T255GS5 |
| Best Sellers Rank | #40,819 in Industrial & Scientific ( See Top 100 in Industrial & Scientific ) #85 in Urethane Adhesives |
| Brand | Fiberglass Supply Depot |
| Brand Name | Fiberglass Supply Depot |
| Color | Black, Clear, Yellow |
| Compatible Material | Vinyl |
| Container Type | Can |
| Customer Reviews | 4.4 out of 5 stars 160 Reviews |
| Full Cure Time | 5 minutes |
| Item Form | Liquid |
| Item Package Quantity | 1 |
| Manufacturer | Fiberglass Supply Depot Inc. |
| Material | Foam , Resin |
| Material Type | Foam,Resin |
| Number of Pieces | 2 |
| Other Special Features of the Product | Versatility |
| Part Number | poly4lbqk |
| Special Feature | Versatility |
| UPC | 819794022897 |
| Unit Count | 64 Ounce |
| Viscosity Level | Medium to High |
| Volume | 2 liters |
| Water Resistance Level | Waterproof |
A**R
Perfect
Works
J**.
Great product! Directions a bit off.
This works great and made a nice, firm filler that I needed for a place on my kayak. It was easily sand-able and paintable. It is firmer/stiffer than the spray foam you buy in cans at the home improvement store. Just be aware that the directions are a bit off. In the video we watched online, it looked as if it foamed up instantly, and the directions said to count a number of seconds and no more before pouring. Our experience was that it took a bit longer for it to foam up, and we wasted some that poured through some holes in the cavity we were trying to fill. I would say an extra 10-15 seconds would have worked better.
M**W
You best be quick!
Good product but on a hot day it goes off QUICK! I used this to backfill fiberglass pool steps that were cracked. I learned on the first mix to not do a lot. The idea was to pour it into the holes I drilled into the stairs that would be patched after. Nope. I had about 3 seconds to get it into the hole as it started going off and most of it would up on the stair. I went out and got funnels for each hole, mixed for 10 seconds and removed the funnel fast. This was better.
T**S
Expands quickly
I created a rear wing which was hollow and needed to strong as it is active and used as an air brake so I needed to fill it with foam. The 4 pound foam was perfect but calculating the internal volume was difficult. To be sure I wasn't going to come up short I added a little extra and did two pours. Because of the shape I couldn't see where the first ended so I proceeded to do the second pour. As soon as I saw it I had like 2 seconds before it over flowed. All good as I planned for this and could just cut the excess off. So be warned and prepared if you mixed too much. It sticks to everything and there is no stopping it. My wing now is as hard as a rock and strong so it worked well for me.
A**N
Didn't roam up, stayed pretty low.
Super dense which was cool I guess but I needed volume which this product did not provide. Could of did something wrong but followed instructions to the letter. Maybe this is not boat filler but maybe used as concrete filler?
T**T
Mixes well
Works well. Use it for my taxidermy projects
J**.
Taxidermy work
Used for taxidermy purposes. It's a denser foam that does not expand as much as the lighter weight foams, but it has been great for form alterations etc Might be a waste to use for habitat work as you'd get more expansion from the lighter weights.
P**N
Easy use closed cell foam mix
Easy to follow instructions, easy to use. I'm buying more.
R**B
Good high quality dense foam.
My first use of this stuff was unconventional. I injected it into the failed diaphragm that engaged the front wheel drive of my 05 Suzuki Grand Vitara. Saved me taking the diff all out and apart. Worked great. Is real dense and firm when cured and seems unaffected by oil. My next unconventional use will be doing some shaping to the front of my Smart Car.
S**O
Works perfectly.
Mix and pour FAST! Works great but the expansion time leaves little to no room for error.
B**I
Great for crafts!
This is great for a craft we found on Pinterest!
P**.
4 Lb. Density Expanding Pour Foam, 2 Part Polyurethane Closed Cell Liquid Foam for Boat and Dock Flo
Does not give the density that I expected. I inserted this foam into PVCt wheels for boat lift. Not worth the money
M**U
Sa gonflé pas fort fort
J'ai mis sa entre mes longerons de bateau et je m'attendais à l'équivalent de 16 litre de mousse comme mentionné sur la bouteille.. Par contre j'en ai eu environ 10 litres.. Je ne suis pas convaincu et je crois que je n'ai pas assez brasser à grande vitesse le mélange.. Donc je devrai en recommander mais Sam semble être un bon produit par contre très coûteux.. Par chance je n'avais pas le bateau au complet à faire!
Trustpilot
2 months ago
2 weeks ago