Cover for Epson 4000 / 4800 Pro inkjet printer & humidity readings

One of the most common suggestions for reducing the incidence of nozzle clogs on Epson 4000 & 4800 inkjet printers is to increase the humidity inside the printer by putting a water soaked sponge in the paper tray and to put an impermeable cover over the top to keep the moisture in. This post is about finding a suitable cover and the humidity results using one gives.

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Various people use polythene or bespoke covers. I could not find a suitable piece of clean polythene and in the UK I could not find any suitable bespoke covers anywhere - not even from Epson, so went looking for an alternative.

I did find one available on the US eBay site so I ordered one, but keen to try to solve my interminable clogging problems I wanted to find something to use now.

I looked around at general printer covers from the likes of Fellowes, but none were anywhere near large enough - the 4800 needs a cover about 850 x 850 x 400mm; much bigger than anything on offer.

I looked at other covers like BBQ covers, but none were remotely like the right dimensions. Eventually I came upon an underbed vinyl storage bag that looked nearly big enough - from Argos, in the UK. If anyone is interested the bag comes in a set of "2 Jumbo Vinyl Storage Bags", Argos' code: 875 0967, costing £3.99 for the pair.

In practice a single bag fits the printer almost perfectly (see photos below) even with 220ml cartridges fitted (or a mix of 220 & 110ml in my case).


I measured the humidity and temperature in the printer head area and outside the printer for the day before putting on the cover and for 2 days afterwards, using an Oregon Scientific Weatherstation with a couple of remote sensors. The temperatures were the same inside and out, but the humidity differed as shown in the the table below.

	Humidity outside printer - %	Humidity inside printer - %
With sponge but no cover	39 - 40	43 - 44
With Sponge and cover	39 - 40	50 - 53

Clearly even without the cover the humidity is higher in the printer due to the water soaked sponge and putting on the cover takes it significantly higher again. Whether these figures actually make a difference only time will tell.

As you can see in the extract below from the User Guide for the 4800, Epson recommend keeping the humidity in various ranges depending on what you want to optimise.


It looks as if a humidity around 40% is at the low end of good and 45-50% is a good range to aim for - so I am happy that my results put my current set up in the right range.

Generally people who report on nozzle clogging problems reckon that the higher the humidity the less the problem - but I have not seen any mention of a practical upper limit. Around 50% would seem a good target to me.

In any case at £2 a time the covers from Argos are a bargain and look better than polythene or bin liners.
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