---
product_id: 282511399
title: "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 Quart Kit)"
brand: "fiberglass supply depot"
price: "$U6641"
currency: UYU
in_stock: true
reviews_count: 5
category: "Fiberglass Supply Depot"
url: https://www.desertcart.uy/products/282511399-fiberglass-supply-depot-4-lb-density-expanding-pour-foam-2
store_origin: UY
region: Uruguay
---

# Closed-cell, water-resistant foam 5 min full cure time 4 lb density for superior buoyancy 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 Quart Kit)

**Brand:** fiberglass supply depot
**Price:** $U6641
**Availability:** ✅ In Stock

## Summary

> 🛠️ Float, fill, and fortify—foam that works as hard as you do!

## Quick Answers

- **What is this?** 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 Quart Kit) by fiberglass supply depot
- **How much does it cost?** $U6641 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.uy](https://www.desertcart.uy/products/282511399-fiberglass-supply-depot-4-lb-density-expanding-pour-foam-2)

## Best For

- fiberglass supply depot enthusiasts

## Why This Product

- Trusted fiberglass supply depot brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Rapid 5-Minute Cure:** Get your projects moving fast with quick setting and minimal downtime.
- • **Resin-Compatible Finish:** Laminates seamlessly with polyester, epoxy, or vinyl ester without melting or damage.
- • **Versatile Application Power:** Perfect for flotation, soundproofing, insulation, and filling voids—one kit, endless solutions.
- • **Precision-Mixed 2-Part Formula:** Ensures consistent, uniform expansion every time for flawless results.
- • **Temperature-Optimized Performance:** Ideal working range of 75°-80°F guarantees maximum expansion and efficiency.

## Overview

Fiberglass Supply Depot’s 4 lb density expanding pour foam is a high-performance, 2-part polyurethane closed-cell liquid foam designed for boat and dock flotation, soundproofing, insulation, and filling voids. This 2-quart kit mixes easily, cures fully in 5 minutes, and offers water resistance and compatibility with various resins, making it a versatile and reliable choice for professional-grade projects.

## Description

Product description

Review: This is the best foam ever!!! - I used the 4 lb foam to make a custom dress form, it did well with a plaster cast you’ll want to paint the inside of the cast with latex paint and use mold release first. The foam is nice and dense! It sands well by hand or with an orbital sander. And it paints well too. You will NEED to use a mixing attachment for your drill!! I tried to mix by hand for a little batch and it did not foam up as much. You will also want to work within the temperature range. If you follow what it says to do it will expand 15x its size. I have bought this 3 times for 2 different custom projects and I will buy again!
Review: Great for repairing old fence - got this to repair a fence post that was searing badly and nearly failed. I dug around it a bit then filled this material in the hole. It did a great repair. Highly recommend it

## 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 1/2 Gallon Kit; Consists of 1 quart of Part A and 1 quart of Part B and produces 1 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

## Technical Specifications

| Specification | Value |
|---------------|-------|
| ASIN | B08T21WRF9 |
| Best Sellers Rank | #255,489 in Industrial & Scientific ( See Top 100 in Industrial & Scientific ) #253 in Urethane Adhesives |
| Brand | Fiberglass Supply Depot |
| Brand Name | Fiberglass Supply Depot |
| Color | Clear |
| Compatible Material | Vinyl |
| Container Type | Can |
| Customer Reviews | 4.6 out of 5 stars 16 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 | soundproofing, insulation, buoyancy, laminating with certain resins without melting |
| Part Number | poly4lbhgk |
| Special Feature | soundproofing, insulation, buoyancy, laminating with certain resins without melting |
| Specific Uses For Product | Flooring, Boat, Dock, Insulation, Soundproofing |
| UPC | 819794022910 |
| Unit Count | 1 Count |
| Viscosity Level | High |
| Volume | 2 Quarts |
| Water Resistance Level | Water Resistant |

## Product Details

- **Brand:** Fiberglass Supply Depot
- **Item Form:** Liquid
- **Material:** Foam,Resin
- **Special Feature:** soundproofing, insulation, buoyancy, laminating with certain resins without melting
- **Specific Uses For Product:** Flooring, Boat, Dock, Insulation, Soundproofing

## Images

![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 Quart Kit) - Image 1](https://m.media-amazon.com/images/I/814gSi7cACL.jpg)
![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 Quart Kit) - Image 2](https://m.media-amazon.com/images/I/8189VtbwU2L.jpg)
![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 Quart Kit) - Image 3](https://m.media-amazon.com/images/I/71Gbm9XW+IL.jpg)
![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 Quart Kit) - Image 4](https://m.media-amazon.com/images/I/71Jn4WV0S0L.jpg)
![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 Quart Kit) - Image 5](https://m.media-amazon.com/images/I/81mbAHsaZfL.jpg)

## Questions & Answers

**Q: i'm new at this.what does density mean i see 2lb 4lb 6lb? thanks**
A: The higher the number, the higher the density equaling stronger flotation.

**Q: How well does this hold up to exposure to water? Applied to the bottom of a boat rear swim platform, for example, to reduce noise?**
A: Not good exposed to the elements.

## Customer Reviews

### ⭐⭐⭐⭐⭐ This is the best foam ever!!!
*by D***N on January 19, 2026*

I used the 4 lb foam to make a custom dress form, it did well with a plaster cast you’ll want to paint the inside of the cast with latex paint and use mold release first. The foam is nice and dense! It sands well by hand or with an orbital sander. And it paints well too. You will NEED to use a mixing attachment for your drill!! I tried to mix by hand for a little batch and it did not foam up as much. You will also want to work within the temperature range. If you follow what it says to do it will expand 15x its size. I have bought this 3 times for 2 different custom projects and I will buy again!

### ⭐⭐⭐⭐ Great for repairing old fence
*by R***H on May 22, 2023*

got this to repair a fence post that was searing badly and nearly failed. I dug around it a bit then filled this material in the hole. It did a great repair. Highly recommend it

### ⭐⭐⭐⭐⭐ Works well
*by J***T on March 18, 2023*

Easy to use and set up well. Product worked predictably and set up uniformly. Another brand I have used in the past started not performing as desired as it had a violent reaction and non uniform results making it unusable. Cost for these smaller bottles was excessive, but at least it worked!

## Frequently Bought Together

- 4 Lb. Density Expanding Pour Foam, 2 Part Polyurethane Closed Cell Liquid Foam for Boat and Dock Flotation, Soundproofing, Filling Voids, and Insulation (2 Quart Kit)
- 6 Lb. Density Expanding Pour Foam, 2 Part Polyurethane Closed Cell Liquid Foam for Boats, Dock Flotation, Carving, Soundproofing, Filling Voids, and Insulation (1 Gallon Kit)
- 4 Lb. Density Expanding Pour Foam, 2 Part Polyurethane Closed Cell Liquid Foam for Boat and Dock Flotation, Soundproofing, Filling Voids, and Insulation (1 Gallon Kit)

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*Product available on Desertcart Uruguay*
*Store origin: UY*
*Last updated: 2026-05-09*