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Fiberglass Supply Depot

Fiberglass Supply Depot 4 Lb. Density Expanding Pour Foam, 2 Part Polyurethane Closed Cell Liquid Foam for Boat and Dock Flotation, Soundproofing, Filling Voids, and Insulation (2 Gallon Kit)

  • Based on 64 reviews
Condition: New
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Availability: In Stock.
Fulfilled by Fiberglass Supply Depot
Arrives Sep 13 – Sep 15
Order within 3 hours and 37 minutes
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Features

  • Flotation Foam is a polyurethane 2-part foam that, when mixed in equal parts and poured in place this foam will soundproof, insulate, or provide extra buoyancy.
  • 4LB. Density polyurethane flotation Foam 2 Gallon Kit; Consists of 1 gallon of Part A and 1 gallon of Part B and produces 4 cubic feet.
  • Once fully cured this foam can be laminated over with any type of polyester, epoxy or vinyl ester resin without melting.
  • The 4LB density also works well in floating decoy or taxidermy applications as well as many other sculpting, casting, carving and other filling applications.
  • All expansion rates and times given are temperature critical. Temperatures below 75 F will lower the expansion rate therefore requiring more foam. Ideal working temperature is 75 to 80 F or above. Accurate measuring of these products is extremely critical. Working time before foaming approx. 45 seconds Time before full expansion: approx. 5 minutes

Features

  • Flotation Foam is a polyurethane 2-part foam that, when mixed in equal parts and poured in place this foam will soundproof, insulate, or provide extra buoyancy.
  • 4LB. Density polyurethane flotation Foam 2 Gallon Kit; Consists of 1 gallon of Part A and 1 gallon of Part B and produces 4 cubic feet.
  • Once fully cured this foam can be laminated over with any type of polyester, epoxy or vinyl ester resin without melting.
  • The 4LB density also works well in floating decoy or taxidermy applications as well as many other sculpting, casting, carving and other filling applications.
  • All expansion rates and times given are temperature critical. Temperatures below 75 F will lower the expansion rate therefore requiring more foam. Ideal working temperature is 75 to 80 F or above. Accurate measuring of these products is extremely critical. Working time before foaming approx. 45 seconds Time before full expansion: approx. 5 minutes

Brand: Fiberglass Supply Depot Inc.


Material: Foam,Resin


Compatible Material: Vinyl


Item Form: Liquid


Item Package Quantity: 1


Package Dimensions ‏ : ‎ 12.2 x 12.2 x 6.5 inches; 20 Pounds


Date First Available ‏ : ‎ January 27, 2021


Manufacturer ‏ : ‎ Fiberglass Supply Depot Inc.


Best Sellers Rank: #75,708 in Industrial & Scientific (See Top 100 in Industrial & Scientific) #91 in Urethane Adhesives


#91 in Urethane Adhesives:


Customer Reviews: 4.4 4.4 out of 5 stars 30 ratings


Material: Foam,Resin


Brand: Fiberglass Supply Depot


Recommended Uses For Product: Flotation, Soundproofing, Insulation, Filling Voids, Sculpting, Casting


Number of Packs: 2


Manufacturer: Fiberglass Supply Depot Inc.


Brand Name: Fiberglass Supply Depot


Number of Packs: 2


Manufacturer: Fiberglass Supply Depot Inc.


Number of Items: 2


UPC: 819794022927


Unit Count: 1 Count


Model Number:


Manufacturer Part Number: poly4lb2gk


Coverage: 4 cubic feet


Material Type: Foam,Resin


Recommended Uses For Product: Flotation, Soundproofing, Insulation, Filling Voids, Sculpting, Casting


Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Sep 13 – Sep 15

Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.

To initiate a return, please visit our Returns Center.

View our full returns policy here.

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Top Amazon Reviews

    • Be mindful of temperature
I used this to repair some damage to a classic 13 Boston whaler. I actually redid the floor and have a word of advice for anyone new to this type of product. Prep your area well and understand the impact ambient temperature has on this foam. While liquid and while mixing/pouring this foam sticks to everything. EVERYTHING. I use masking tape and those cheap brown rolls of contractor paper to make sure the only thing exposed to the foam before and after expansion is the hole I’m pouring into. Regarding the temperature: the hotter it is outside the faster the foam mixes and needs to be poured. Also the hotter it is outside the more your foam will expand overall. I tried filling a small hole on a 70 degree day and the foam performed well. I thought….. the next week I filled a similar sized hole and used the same amount of foam. Only difference was the temperature outside was in the 90’s. I had the foam expand at least twice as far and ooze out all over the place. Just be mindful of them temp and as expensive as this foam is I suggest doing it on the hottest days you can so that you get the most expansion. ... show more
Reviewed in the United States on June 26, 2026 by Tcollins
    • Expanding Foam
Product works as described Using on motor coach void areas
Reviewed in the United States on June 1, 2026 by George Gaspar
    • Works
Does what it needs to do
Reviewed in the United States on March 10, 2026 by John
    • This stuff does the job
I was using this to void fill a vintage boat project. This stuff did the trick and was cheaper than some competitors. Listen to the instructions and it will work. After the foam hardens it is very sturdy and won’t be going anywhere. Yes it is somewhat messy but for an efficient way of void filling it was worth it. ... show more
Reviewed in the United States on November 10, 2023 by Joe Meyer
    • Follow the directions
Good stuff. Works well. Read the direction AND HEED THEM! (It hardens FAST)
Reviewed in the United States on September 20, 2025 by tch
    • Works as described
Works exactly as described as long as you follow instructions. I did a test batch and it didn’t turn out so good. I then put on a space heater and made sure the temperature was above the recommended 75-80F and mixed the two compounds as instructed. It worked perfectly for my DIY project, couldn’t be happier as it saved me a lot of headache. A word of warning though it hardens very quickly and becomes hard as a rock. Make sure you prepare the surface and block off anywhere you don’t want it to go. Act quickly and it will turn out well, once you pour there’s no redo. ... show more
Reviewed in the United States on January 31, 2022 by Michigancarguy81
    • Lots of Rigid Foam per Dollar
Great foam, as described, great deal!
Reviewed in the United States on September 6, 2025 by tat
    • Good foam
Works as should
Reviewed in the United States on March 16, 2025 by Josh Saville

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