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When & how to shade a greenhouse

When you’re growing your own in your greenhouse, protecting your plants from extremes of temperatures will keep them healthy and growing well.

Keeping a thermometer in your greenhouse will help guide you to the right time to add shading to protect seedlings and plants from heat of the sun. RHS guidelines recommend that temperatures don’t exceed 27°C /81°F, otherwise tissue damage can occur.

Sun-flag (partial collapse that looks like wilting), leaf scorch and desiccation can all be signs of plants and seedlings struggling with high temperatures.

Shading with Thorndown Peelable Glass Paint is the perfect way to easily apply shading to greenhouses and has the added advantages of looking nicer than traditional shading paint, and is nice and easy to remove. At the end of the season simply pick at a corner and peel off the entire sheet!

Try to resist putting shading up too soon as seeds need plenty of light to germinate and seedlings need sunlight to grow. April is normally the month when the sun starts to increase in strength and intensity and can often reach high temperatures that require shading towards the mid and end of the month.

However, the cold and humid nights can cause extended delays with the drying process and can cause the Peelable Glass Paint coating to slip if any rain comes before the paint has totally cured and bonded to the window surface. Wait until weather conditions are consistently warm with a strong sun.

Tips for Painting Peelable Glass Paint Externally

When painting externally it is always recommended to make sure no rain is forecast within 24 hours of application. When painting glass paint onto glass or plastic materials this is even more essential, as the paint coating has to bond to a slippery surface.

Do not apply when night time temperatures are cold and humidity and condensation levels are high.

These poor night conditions will negatively impact on the drying process and although the coating will appear dry and be touch dry, it will not cure and bond to the glass properly.

If the paint hasn’t had enough time to dry and bond completely, any rain can get under the coating causing slippage, or break it down, and/or wash it off.

 If you are applying a 2nd coat to external panes whether on the interior or exterior, then you need to allow a greater period of time for the 1st coat to bond and fix properly. We recommend leaving to dry for 24 hours before applying a 2nd coat and in cooler damper months such as early spring, late autumn and winter, leave the 1st coat for 48 hours before applying a 2nd coat. If the 1st coat hasn’t fully fixed and you apply a 2nd coat too soon, you are making the 1st coat wetter, extending the drying time greatly and can destabilise the coating leading to slippage.

You can download a pdf of Application Advice here.

For best results apply with a roller using a foam sleeve. Brush strokes show up when light shines through the coating.

If painting internally condensation can have the same effect although you can minimise the risk by painting at the start of the day. Make sure the pane is clean and dry, roller on a single coat and keep windows and doors open to allow plenty of ventilation to help with the drying process.


You can be selective in where you apply shading. Sometimes you only need to apply shading to the roof panes, or south-facing panes. You can also paint the shading on and remove it if the weather conditions become consistently poor and cloudy, or if you’ve moved plants around and need more light in certain areas.

Partial shade can also be provided by painting on stencils or stripes to panes so the plants still get a chunk of light but at a greatly reduced intensity. In the above pictures a swan stencil was used to create pretty decorative shading. Once the Swan White Peelable Glass Paint had been applied to the roof panes, the wet roller was used with the stencils. As there wasn’t too much paint on the roller, the paint didn’t bleed underneath the stencil and the perfect swan was made.

Peelable Glass Paint comes in  24 opaque colours so you can match your wood work to your shading colour, and 14 Translucent colours to create stained glass decorative effects.

In the greenhouse below, shading has been applied to the roof panes but other windows and the doors left so that heat and sun loving plants such as chillis and tomatoes can get maximum sun throughout the day.


Normally you would start to reduce and remove shading at the end of the season around September time, or earlier if you’re growing heat loving plants such as chillis and aubergines.

With Thorndown Peelable Glass Paint you just pick at an edge of the coating until you get some of the film between your fingers, then grip it and peel it off!

Thorndown Peelable Glass Paint does create a hard-wearing long-lasting coating so if you like it, you can leave it on as a permanent coating. If the coating has been left on for a long time it can have dried out and be difficult to peel off. The coating can also dry out if it’s on a south-facing polycarbonate or acetate window.

Thin coatings are more susceptible to drying out and exterior coatings can be eroded by the weather.

If the coating does dry out then the elasticity will have gone. To restore it you can soak it with water, leave for about 15 minutes then when the elasticity has been restored, pick and peel. You can use a wet cloth or sponge, plant mister, or if external then you can use a hose pipe to soak it.

When this doesn’t work you can paint on another coat and leave to dry for 24-48 hours. This coating will bond to the old coating underneath and when you peel it off, it will take the old coating off with it.

On glass windows you can use a paint scraper but we wouldn’t advise this on polycarbonate, acetate or other plastics as it can scratch the surface.

If the above methods don’t work you can use a soap solution with a high ph value, like a dilute alkaline soap solution. We have found that household kitchen bleach sprays also work well. Soak the coating with the solution/spray and leave to work for 5-10 minutes, then you should be able to wipe the old coating off with a cloth. In extreme or rare cases solvent strippers can be used.

You can download a handy pdf guide with application advice and removal tips.