The secret to a fast, fun slip and slide comes down to two things: a slick surface material and the right lubricant on top. Water alone isn’t enough. You need a soap or lubricant layer between the plastic and your body to reduce friction, and you need to keep water flowing continuously so that layer never dries out.
Choose the Right Plastic
The material you slide on matters more than anything you put on it. Thin tarps and cheap painter’s plastic wrinkle, drag, and tear, all of which slow you down. For a backyard setup, look for polyethylene sheeting at least 6 mil thick from a hardware store. If you want something that lasts multiple summers, heavy-duty HDPE (high-density polyethylene) sheeting in the 60 to 80 mil range is what commercial hill slides use. It’s naturally smooth and low-friction, meaning you glide faster even before adding soap. A standard roll of 6 mil plastic from a home improvement store costs under $30 and works well for a single season.
Lay the plastic out so there are no wrinkles or folds. Wrinkles create friction points and can also cause skin burns at higher speeds. If you’re working on grass, mow the lawn short first, then walk the area to check for rocks, sticks, or anything sharp that could poke through. Smooth, freshly mowed grass is your ideal base.
Use Baby Shampoo, Not Dish Soap
This is the most common mistake people make. Dish soap seems like the obvious choice because it’s slippery and cheap, but it’s concentrated detergent designed to cut grease. When it splashes into eyes, it causes real pain and irritation, especially for kids. Tear-free baby shampoo creates the same slick surface without the sting. A single bottle spread across the plastic and refreshed every 15 to 20 minutes keeps things moving.
To apply it, squeeze a generous line of baby shampoo down the center of the plastic, then spread it around with your hands or feet while the water is running. You want a thin, even layer across the entire sliding surface, not just a blob at the start. The shampoo mixes with the running water to form a continuously slippery film.
Keep Water Flowing the Entire Time
A slip and slide that dries out for even a minute becomes a skin-burn hazard. Set up a garden hose or sprinkler at the top of the slide so water runs down the full length continuously. If you have a second hose, position it at the midpoint to prevent dry patches in the center, which is where most slides lose speed.
The water does two jobs: it activates the soap layer, and it creates a thin hydroplaning film between your body and the plastic. Without constant water flow, even the best lubricant gets patchy and sticky. If you notice people slowing down or stopping short, the first fix is always more water, not more soap.
Add Glycerin for Extra Speed
If baby shampoo and water aren’t slippery enough, vegetable glycerin is the upgrade. It’s a thick, clear liquid sold at pharmacies and craft stores for a few dollars a bottle. Glycerin is non-toxic, skin-safe, and significantly more slippery than soap alone. Mix a few tablespoons into a bucket of water, then pour it down the slide or spray it on with a garden sprayer.
Glycerin works because it holds moisture on the surface rather than letting it run off. This creates a persistently slick layer that lasts longer between reapplications. It also doesn’t foam up the way soap does, so you get a cleaner sliding experience. Some people combine baby shampoo and glycerin together for maximum effect: the shampoo provides initial slip, and the glycerin keeps things lubricated between water refreshes.
Use a Gentle Slope
A slight downhill grade does more for speed than any amount of lubricant. You don’t need a steep hill. Even a gentle slope of a few feet over a 50-foot run gives you enough momentum to slide the full length without a running start. On completely flat ground, you’ll always need a faster running approach, which increases the risk of falls at the entry point.
If your yard is flat, you can create a small mound of dirt or sand at the start to give sliders a downhill launch. Just make sure the transition from the mound to the flat section is smooth, with no abrupt drop-offs. Anchor the top of the plastic with tent stakes or heavy rocks wrapped in towels (so there’s nothing hard exposed on the sliding surface), and leave plenty of extra plastic at the end as a runoff zone.
How to Reapply During Use
Even with the best setup, you’ll need to refresh the lubricant layer periodically. Every 15 to 20 minutes, pause sliding for a quick reapplication. Squeeze more baby shampoo onto the surface, spread it with a push broom or your feet, and let the hose run for 30 seconds before anyone slides again. If you’re using glycerin, reapply that at the same time.
Watch for signs that the surface is losing its slick: people slowing down in the same spot, visible dry patches, or the plastic feeling tacky when you touch it. High temperatures and direct sun dry out the surface faster, so on hot days you may need to reapply every 10 minutes. Keeping a filled spray bottle of soapy water nearby makes quick touch-ups easy between full reapplications.
What to Avoid
- Cooking oil or vegetable oil. It sounds logical, but oil breaks down plastic over time, creates a mess that’s nearly impossible to clean off grass, and makes the slide dangerously uncontrollable. Soap-based lubricants give you slippery without reckless.
- WD-40 or silicone sprays. These are petroleum-based products not meant for skin contact. They also stain clothing permanently and kill grass.
- Too much soap at the entry point. If the run-up area is soapy, your feet slip before you’re ready. Keep the first few feet of plastic wet but soap-free so sliders can get a stable running start before hitting the lubricated zone.
The combination of smooth polyethylene plastic, tear-free baby shampoo, continuous water flow, and an optional glycerin boost will give you the fastest, safest backyard slide you can build. The whole setup takes about 20 minutes, and most of that time is spent clearing the ground and unrolling the plastic.