---
product_id: 766162487
title: "Fiberglass Supply Depot 4 Pounds. Density Expansion Foam, 2-Part PU Closed Cell Liquid Foam for Boat Flotation and Dock, Acoustic Insulation, Vaz Fill"
brand: "fiberglass supply depot"
price: "5988439₫"
currency: VND
in_stock: true
reviews_count: 5
category: "Fiberglass Supply Depot"
url: https://www.desertcart.vn/products/766162487-fiberglass-supply-depot-4-pounds-density-expansion-foam-2-part
store_origin: VN
region: Vietnam
---

# 45 sec working time, 5 min full expansion 4 lbs density for firm support Closed-cell PU foam for flotation & insulation Fiberglass Supply Depot 4 Pounds. Density Expansion Foam, 2-Part PU Closed Cell Liquid Foam for Boat Flotation and Dock, Acoustic Insulation, Vaz Fill

**Brand:** fiberglass supply depot
**Price:** 5988439₫
**Availability:** ✅ In Stock

## Summary

> 🛠️ Elevate your projects with foam that’s as tough as your ambition!

## Quick Answers

- **What is this?** Fiberglass Supply Depot 4 Pounds. Density Expansion Foam, 2-Part PU Closed Cell Liquid Foam for Boat Flotation and Dock, Acoustic Insulation, Vaz Fill by fiberglass supply depot
- **How much does it cost?** 5988439₫ with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.vn](https://www.desertcart.vn/products/766162487-fiberglass-supply-depot-4-pounds-density-expansion-foam-2-part)

## 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

- • **Compatible with Resins:** Seamlessly laminates with polyester, epoxy, or vinyl ester resins without melting or damage.
- • **Rapid Expansion & Cure:** Fully expands in 5 minutes and cures to a rock-solid finish ready for sanding and painting.
- • **Firm & Reliable Support:** 4LB density delivers superior strength for moderate load-bearing applications like boat decks and gas tank supports.
- • **Precision Working Window:** 45 seconds to apply before foaming starts, ensuring you control the perfect pour every time.
- • **Versatile Multi-Use Foam:** Ideal for flotation, acoustic insulation, sculpting, casting, and taxidermy—one foam, endless possibilities.

## Overview

Fiberglass Supply Depot’s 4LB Density Expansion Foam is a high-performance 2-part closed-cell polyurethane foam designed for flotation, soundproofing, and structural support. With a precise 45-second working time and full expansion in 5 minutes, it cures into a firm, sandable, and paintable solid compatible with various resins. Perfect for boat flotation, dock repairs, and creative applications like sculpting and taxidermy, this foam offers professional-grade durability and versatility for demanding projects.

## Description

This 4LB density foam is suitable for most float applications that require more support than that of 2LB offers. This foam is recommended for use on gas tank support and some deck areas. Choose this density if you think the foam will need to withstand light to moderate loads. The density of 4LB also works well in floating bait or taxidermy applications, as well as many other sculpting, casting, notching and other filling applications.

Review: 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.
Review: 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.

## Features

- Flotation Foam is a 2-part polyurethane foam that, when mixed in equal parts and put in place, this foam will be soundproof, insulate or provide extra buoyancy.
- 4 lbs. Quart Density Polyurethane Flotation Foam Kit; Consists of 1 Liter of Part A and 1 Liter of Part B and produces 1/2 cubic foot.
- Once fully cured, this foam can be laminated with any type of polyester, epoxy or vinyl ester resin without melting.
- 4LB density also works well in floating bait or taxidermy applications, as well as many other sculpting, casting, carving and other filling applications.
- All provided expansion rates and times are temperature critical. Temperatures below 75° F will decrease the expansion rate, therefore requiring more foam. Ideal working temperature is 75° to 80° F or higher. Accurate measurement 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 | B08T255GS5 |
| Manufacturer | Fiberglass Supply Depot Inc. |
| Manufacturer reference | poly4lbqk |
| Package Dimensions | 20.57 x 13.72 x 8.89 cm; 1.38 kg |

## Product Details

- **Brand:** Fiberglass Supply Depot
- **Item form:** Liquid
- **Material:** Foam, Resin
- **Special features:** Heat Resistant, Versatile
- **Specific uses for product:** Flotation, Decoy, Taxidermy, Sculpting, Casting, Carving, Filling

## Images

![Fiberglass Supply Depot 4 Pounds. Density Expansion Foam, 2-Part PU Closed Cell Liquid Foam for Boat Flotation and Dock, Acoustic Insulation, Vaz Fill - Image 1](https://m.media-amazon.com/images/I/81XhbU5HAlL.jpg)

## Questions & Answers

**Q: What is the cure time?  I see 5 minute until "full expansion" but nowhere on the package do I find the cure time.**
A: Around 30-60 minutes

**Q: If one doesn't use the whole kit how long will the 2 parts last?**
A: As long as you make them.

**Q: would this provide floatation if used in the bow of a kayak?**
A: Yes, that is one of its intended uses. It is a closed cell foam.

**Q: Question any way to pump this? I have a void under a concrete walkway and I need to get it back 4 feet The void is 4x4 and 2 to 6 inches deep.**
A: You only have a brown 30 seconds after you mix the product to put it in the location that you are wanting depending on temperature if you have a mixing tip then you could pump it however it needs to be agitated for 20 seconds

## Customer Reviews

### ⭐⭐⭐⭐⭐ Review
*by J***. on 3 August 2024*

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.

### ⭐⭐⭐⭐⭐ Review
*by T***S on 4 January 2024*

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.

### ⭐⭐⭐⭐⭐ Review
*by R***D on 21 October 2024*

I purchased this product to secure a fuel tank in a boat. It worked perfectly. I carefully followed the instructions, adding part A to part B (not the other way around), working in an ambient temperature of about 70 degrees Fahrenheit. It expanded slowly over a few minutes and did not "explode" as described by others. The instructions emphasize the mixing order, and I suspect that is the key to avoiding disaster.

## 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 (Quart Kit)
- Fiberglass Supply Depot 6LB Density Expanding Pour Foam, 2 Part Polyurethane Closed Cell Liquid Foam for Boats, Dock Flotation, Carving, Soundproofing, Filling Voids, and Insulation (Quart Kit)
- 2 Lb Density Expanding Pour Foam, 2 Part Polyurethane Closed Cell Liquid Foam for Boat and Dock Flotation, Soundproofing, Filling Voids, and Insulation (Quart Kit)

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*Product available on Desertcart Vietnam*
*Store origin: VN*
*Last updated: 2026-06-05*