This is what ITG say from their website.
Instructions for cleaning, maintaining and
re-oiling itg Hand Made Panel Air Filters
Cleaning
This hand made panel filter is pre-oiled with Silkolene foam spray oil and will last for many thousands of miles depending on the conditions that the vehicle being used is in, before requiring to be cleaned.
The best way to clean the filter is to use a Silkolene Cleaning Fluid or suitable solvent to remove the dust/dirt contaminants.
You could also clean the filter in a bath of petrol if
necessary. (NOTE: Always use suitable protective equipment).
The adhesives and material used in the filter are petrol resistant but the adhesives are not totally water-resistant so washing in warm water is tolerated but under no circumstances should the filter be left to soak as in time this will break down the adhesive.
Water encountered in normal use (i.e. rain, spray etc) will have no adverse effect on the filter.
First when the filter has seen a heavy soiling or build up use a Vacuum cleaner by running the nozzle over the dirty foam side of the filter drawing the dust out of the filter the way that it entered the filter.
Then put the filter into a basin or tray large enough to allow the filter to be submerged. Now immerse the filter (foam side down) in the cleaning solvent and agitate so that the solvent goes into the filter foam and draws the dirt/dust out in the solution.
Once you are happy that all of the oil residue has been removed by the solvent dispose of the solvent in the appropriate manner (at a recycling tip or similar but not down the household drain system).
Now apply water either by a tap or hose onto the filter and allow the water to flow through the mesh side of the filter to remove all the cleaning solvent and any other dust/dirt residue.
Now use sufficient washing-up liquid over the filter surface and massage it in to create a lather using the tips of your fingers to encourage the remaining dirt/dust out of the filter. You will notice the dirt coming out in the colour of the lather.
After a minute or so wash this through thoroughly with water and repeat the cycle again using the washing up liquid to get the filter really clean.
You will be able to feel any large debris with your fingers and work this out with the water. (NOTE: If the filter is still soiled you could use a nail brush or similar to create circular motions over the entire surface of the filter which will help to remove the heaviest of deposits in particular if you use the
vehicle for off road racing).
Make sure that the filter is rinsed well with clean water running through the filter from the mesh side until no soap residue is obvious. Once this has been done massage any of the excess water out of the filter and if necessary take the filter outside and shake it to help remove any further water deposits.
The filter should then be left in a dry, warm environment to dry naturally.
Re-oiling:
Once the filter is dry (NOTE: Do not use a high pressure air line or heat gun to speed the process up). Re-oil with Silkolene Foam filter Spray Oil which is straight forward and follow the manufacturers instructions on the can to do this.
